Add an empty .npmignore file in an attempt to fix error with running bower install as a postinstall script when deploying to heroku.

See: https://github.com/heroku/heroku-buildpack-nodejs/issues/91
Adjust .bowerrc to use temp directories that are local to the project root in an attempt to fix ENOENT/ENOTEMPTY errors with heroku deployment.

Reference:
https://github.com/bower/bower/issues/933