Set main to source usertiming.js

The `main` property should not be a minified file as recommended by the bower specification.

https://github.com/bower/bower.json-spec#main
Rename bower package to "usertiming"
Merge pull request #3 from josh/main

Set main to source usertiming.js
Merge pull request #4 from josh/bower-package-name

Inconsistent bower package name: use usertiming instead of usertiming.js
Merge remote-tracking branch 'upstream/master'