cleanup, fixes

Hey. You've done good job, this module helped me much. Nevertheless, I've strikes some issues. Here are fixes.

https://github.com/podgorniy/node-jenkins-api/commit/5e160b0f22ca5acfb36099c502051ef9b9598473
General fixes. I've updated code to look more javascript-like (with vars, and properties access), made it [strict](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Functions_and_function_scope/Strict_mode). This should simplify further development, because will reduce scope of possible issues.

https://github.com/podgorniy/node-jenkins-api/commit/a28b56bcb476632cc2cb3d52200b92a97a997287
**build_info** method did not form correct url for request. I assume, that's because of `BUILD` template string, which is not expected to be used with this method. So I created new template string for this method.

https://github.com/podgorniy/node-jenkins-api/commit/5b6b83e88e746d369d50266656fc2502837a71f5
**last_completed_build_info** `LAST_REPORT` string had unnecessary part of url, I guess, from your local testing. So you requests to local server might passed correctly, but not for external. (BTW I used http://jenkins.nodejs.org for testing)