Fix for #73: proper sys.exit code when restarting buildout

Fixing docstring incorrect reference to obsolete command line options

Add support to ignore sections conditionally based on a Python expression.

Fixes https://github.com/buildout/buildout/issues/94

Add bin/buildout --version

A restarted project's exit code is now properly propagated. This makes
buildout more reliable in automatically-run situations.

When the process is restarted (and results in an error),
we can now properly check the exit code that comes out of
the 'root' buildout process.

Made tests independent of distribute version number

Replaced the fixed distribute version number with the currently valid one by
just asking for the current version and inserting that in the various spots we
need it in this testfile

the current distribute version).

Use umask when doing "chmod +x". Improved version of pull request #18

PEP8 changes for bootstrap.py

I changed a few things to allow for better pep8 compatability.

Section titles can now have this form:
 [sectionname:Python expression] # optional comment

If the Python expression evals to False, the section will be ignored.

Expressions have some defaults to support common conditions such as:
 [sectionname: not windows] # ignore this section on windows

Section title lines in the traditional form are still supported of
course:
 [sectionname] # optional comment 
or
 [sectionname] ; optional comment 

os.umask is a bit weird in that it *does* return the current umask,
but it has a required argument that it immediately sets as the new umask...
Weird. Distribute solves that by assigning a dummy value and re-setting
the umask to the original value.

The matching test verifies that it actually works.

Note that I use python 2.6+'s octal notation: 0o755.
Buildout 2 doesn't support python 2.5 anymore, iirc, so that's fine.

Note: includes if/else for windows.
Uses http://docs.python.org/2/library/os#os.access

A fixed (0755) execute permission is used in two places, I refactored it into
one method. Bonus: this makes it easy to test the fix proposed in
https://github.com/buildout/buildout/pull/18

Corrected travis image link

Fix for #71 - looks good to me.

Picked versions are stored for later printing/writing in the Installer
also when show-picked-versions is set to false but update-versions-file is set
to a file. Previously, show-picked-versions=false would also disable the versions
file updating.

I changed it to make it applicable whether the picked versions
are printed or not. 'This info has been written to' doesn't work
if this hasn't been printed on the previous lines :-)

`update-versions-file = true` has no effect when `show-picked-versions` is
false.

The old "hashbang" url redirected to https://travis-ci.org//buildout/buildout, with two slashes, which didn't work. Travis bug, but using the new https://travis-ci.org/buildout/buildout url ourselves is easier :-)

Prep for release.

Provoke a travis-ci run. :)

Fix for #64: __pycache__ dir inside distutils scripts metadata directory

Reinout distutils script encoding fix for #65

Should never ever happen, of course, but somewhere in the universe exists a
distutils script with just the `#!bin/python` line... Added a len() to guard
against that.