add some http convenience functions
flesh out the approach a little more: embedding model types into the main
Trello type.
add Member and a couple of methods.  also set out some common interfaces
and constants for use by all the model types. Not sure this will work well
so this may change.
make some common functions/types with tests
got first api request looking reasonable (against the test, anyway)
Merge branch 'master' of https://github.com/aggieben/trello

# By Benjamin Collins (5) and waffle.io (1)
* 'master' of https://github.com/aggieben/trello:
  Update README.md
  add waffle.io badge
  Update README.md
  Update README.md
  Update README.md
  add build status to readme