Add basic initial CONTRIBUTING.rst per github guidelines. Add badges for landscape.io.

[skip ci]

CONTRIBUTING.rst

+Basics
+======
+
+Please see `contribution-guide.org <http://www.contribution-guide.org/>`_ for
+general details on what we expect from contributors. Thanks!
+
+
+gevent-specific details
+=======================
+
+There are a number of systems in place to help ensure gevent is of the
+highest possible quality:
+
+- Builds on Travis CI automatically submit updates to `coveralls.io`_ to
+  monitor test coverage. Pull requests that don't feature adequate test
+  coverage will be automatically failed.
+
+.. image:: https://coveralls.io/repos/gevent/gevent/badge.svg?branch=master&service=github
+   :target: https://coveralls.io/github/gevent/gevent?branch=master
+
+- Likewise, builds on Travis CI will automatically submit updates to
+  `landscape.io`_ to monitor code health (adherence to PEP8, absence of
+  common code smells, etc). Pull requests that decrease code health will
+  be automatically failed.
+
+.. image:: https://landscape.io/github/gevent/gevent/master/landscape.svg?style=flat
+   :target: https://landscape.io/github/gevent/gevent/master
+   :alt: Code Health
+
+- A test suite is run for every push and pull request submitted. Travis
+  CI is used to test on Linux, and `AppVeyor`_ runs the builds on
+  Windows. Pull requests with tests that don't pass will be
+  automatically failed.
+
+.. image:: https://travis-ci.org/gevent/gevent.svg?branch=master
+   :target: https://travis-ci.org/gevent/gevent
+
+.. image:: https://ci.appveyor.com/api/projects/status/q4kl21ng2yo2ixur?svg=true
+   :target: https://ci.appveyor.com/project/denik/gevent
+
+.. _landscape.io: https://landscape.io/github/gevent/gevent
+.. _coveralls.io: https://coveralls.io/github/gevent/gevent
+.. _AppVeyor: https://ci.appveyor.com/project/denik/gevent
+
+Pull requests that don't pass those checks will be automatically
+failed. But don't worry, it's all about context. Most of the time
+failing checks are easy to fix, and occasionally a PR will be accepted
+even with failing checks to be fixed by the maintainers.

MANIFEST.in

@@ -9,6 +9,7 @@ recursive-include util *
 include LICENSE
 include NOTICE
 include README.rst
+include CONTRIBUTING.rst
 include TODO
 include changelog.rst
 include MANIFEST.in

README.rst

@@ -99,16 +99,26 @@ something like this::
   coverage html -i
   <open htmlcov/index.html>
 
-Builds on Travis CI automatically submit updates to `coveralls.io`_.
+Builds on Travis CI automatically submit updates to `coveralls.io`_ to
+monitor test coverage.
 
 .. image:: https://coveralls.io/repos/gevent/gevent/badge.svg?branch=master&service=github
    :target: https://coveralls.io/github/gevent/gevent?branch=master
 
+Likewise, builds on Travis CI will automatically submit updates to
+`landscape.io`_ to monitor code health (adherence to PEP8, absence of
+common code smells, etc).
+
+.. image:: https://landscape.io/github/gevent/gevent/master/landscape.svg?style=flat
+   :target: https://landscape.io/github/gevent/gevent/master
+   :alt: Code Health
+
 Continuous integration
 ----------------------
 
 A test suite is run for every push and pull request submitted. Travis
-CI is used to test on Linux, and `AppVeyor`_ runs the builds on Windows.
+CI is used to test on Linux, and `AppVeyor`_ runs the builds on
+Windows.
 
 .. image:: https://travis-ci.org/gevent/gevent.svg?branch=master
    :target: https://travis-ci.org/gevent/gevent
@@ -134,3 +144,4 @@ CI is used to test on Linux, and `AppVeyor`_ runs the builds on Windows.
 .. _AppVeyor: https://ci.appveyor.com/project/denik/gevent
 .. _what's new: http://www.gevent.org/whatsnew_1_1.html
 .. _changelog: http://www.gevent.org/changelog.html
+.. _landscape.io: https://landscape.io/github/gevent/gevent

dev-requirements.txt

@@ -6,4 +6,8 @@ prospector[with_pyroma]
 coverage>=4.0
 coveralls>=1.0
 cffi
+# For viewing README.rst (restview --long-description),
+# CONTRIBUTING.rst, etc.
+# https://github.com/mgedmin/restview
+restview
 -e .

setup.py

@@ -405,6 +405,7 @@ else:
 
 # If we are running info / help commands, or we're being imported by
 # tools like pyroma, we don't need to build anything
+_BUILDING = True
 if ((len(sys.argv) >= 2
      and ('--help' in sys.argv[1:]
           or sys.argv[1] in ('--help-commands',
@@ -413,6 +414,7 @@ if ((len(sys.argv) >= 2
                              'clean',
                              '--long-description')))
     or __name__ != '__main__'):
+    _BUILDING = False
     ext_modules = []
     include_package_data = PYPY
     run_make = False
@@ -531,5 +533,5 @@ except BuildFailed:
         raise
     ext_modules.remove(ARES)
     run_setup(ext_modules, run_make=run_make)
-if ARES not in ext_modules and __name__ == '__main__':
+if ARES not in ext_modules and __name__ == '__main__' and _BUILDING:
     sys.stderr.write('\nWARNING: The gevent.ares extension has been disabled.\n')