Add missing context.cpp file.
Various spelling and grammar fixes in README.rst

Tidied up a lot of sentences to make them more clear. Fixed a few
spelling mistakes.
Merge pull request #2 from thethomaseffect/master

Fixed a few spelling and grammar mistakes in README.rst
Merge branch 'master' of git://github.com/niwibe/phantompy into make_osx
Changes:
- introduce use of cffi to get around ctypes being bizarrely fragile in OSX
- update image handling to use cffi or fallback to ctypes code
- add in uninstall target
- add in OSX target for use with brew.
- remove unused dependencies
oops. PEP8 scanner says image, webelements, ctyles, lib are unused. remove
TODO - kill ctypes. It creates more cruft than pythonic fun