Fixed a few issues, broken tests, upgraded some modules,

 - Fixed reverse-compatibility issue with how we process the arguments for the callback in airbrake.notify (https://github.com/felixge/node-airbrake/commit/f1ac2dd58e1ee3d781ef63e0158713248a1b5bce)
 - Fixed a bunch of broken tests
 - Upgraded the following modules
  - request to 2.21.x
  - xmlbuilder to 0.4.x
  - sinon to 1.7.x
- No longer using makefile
- npm test now works
- added support for calling ./test/run.js and run only specific tests or customize verbosity 
- fixed double-quoting issue - https://github.com/felixge/node-airbrake/issues/11