Add Bower package definition

Add support for fit.js to be included as a Bower front-end package. See
http://bower.io for more info. Create bower.json file that defines the
package. Once committed to master, the package can be registered officially
with Bower by running the following command (with bower installed):
bower register fit.js https://github.com/soulwire/fit.js.git
Merge pull request #3 from mwindle/mwindle/bowersupport

Add Bower package definition