Readme: Update Python versions to match compile

Also matches recent updates to https://devcenter.heroku.com/articles/python-runtimes
Update pylibmc to support nested requirements.

The current regex assumes that pylibmc appears at the beginning of a line
(whitespace only precedes it), which is a fair assumption in a single 'flat'
requirements.txt file. However, if you are using nested requirements then
this is not the case - your pylibmc may exist in a sub-directory. This is
very similar to the way in which mercurial is installed if "hg+" is found
in the requirements file (see the /bin/compile script). By insisting that
pylibmc appear at the beginning of the file, it's impossible to fool the
compilation into installing libmemcached (as this script does) by simply
putting the phrase into a comment, which is what you *can* do with 'hg+'.

I've updated the regex to remove the beginning of line restriction. This
means that you can add a comment to a top-level requirements.txt that
will trigger the install, without having to functionally alter your
nested requirements.

e.g. top-level requirements.txt:

    # fake comment to trigger pylibmc script
    # fake comment to trigger hg+ install
    -r requirements/production.txt
Merge pull request #152 from yunojuno/master

Update pylibmc to support nested requirements.
Merge pull request #150 from cclauss/patch-2

Readme: Update Python versions to match compile
python-2.7.8 (--shared)
update readme with new python versions
merge
Default Python: 2.7.8
python 3.3.5
libffi attempt
follow redirects
add autoconf
new libffi attempt
update of autoconf
libffi
autoconf formula
pypy 2.0
libffi: --enable-shared
pypy v2.3.1
ld_library_path?