Copy over example extension files
Update README.md formatting
Use POSIX shell script syntax for portability

See: https://github.com/hhvm/example/pull/3
Changed files according to Jeremy's suggestions
1) README modeled after other Extension APIs
2) Changed name of extension to mongo
3) Still not quite sure about the config.hdf file, so put in both methods
on the README.md
Merge pull request #1 from 10gen-labs/test_extension

Test extension added