Review : Zlib::Deflate fix

Tomas, if you sync to [email protected]:shri/ironruby.git and run
Languages\Scripts\bat\dev.bat, you should be able to run this command to
get a much better diffing experience. For this change, the URL above is
simpler though as there is only one .cs file with changes.
gitdiff bc39b55623db150ba7b58b95787f2f61d8f5840b

Fixed Zlib::Deflate algorithm to use the right header and footer around
Added GitDiff.bat to use windiff for diffing, and to be able to get of
files to diff from rather than having to go serially through all the
files one by one
Adds a trivial README - will automatically show the contents
inline if anyone browses the repo.