Exit on test failure

When test fails, it should not continue to run other commands.
Fixes #891

Revert #853 implicit wildcards in MANIFEST.in

This reverts commit 23aba916.

As sometimes orig_path may be something other than a list (i.e. _NamespacePath), use iterator tools to sort the items in place. Fixes #885.

Add test capturing expectation when a package is both installed and in the current working directory. Ref #885.

Use py.test to launch pytest, rather than python -m test, preventing the empty path from being added to sys.path per pytest-dev/pytest#2104. Fixes #852. Also use 'usedevelop' as the setuptools.tests.fixtures aren't available in a standard install.

docs: reorder ToC; update stray Bitbucket links