Add npmignore and fix Travis deploy settings

AngularFire isn't actually on npm (https://www.npmjs.org/package/angularfire) since the tagged build for 0.8 timed out. This:

* Adds an `.npmignore` file so the published tar isn't bloated by bower components and tests among other utility files
* Fixes the npm deploy configuration in `.travis.yml` — Travis defaults deploy tasks to master and will complain that a tagged build is on a disallowed branch since it has no branch