Library browserify

Some key changes:

* More specific about real dependencies: https://github.com/CartoDB/torque/commit/936bfe227a23aa150f4a1e6102f7051716fce2f9
* Removes underscore dependency: https://github.com/CartoDB/torque/commit/e8634abc0da863ccad558bd59be5cdeb20acddc8 and https://github.com/CartoDB/torque/commit/3471a2ac6d2fb93da631989c2c51135f4d8a70c9
* Tests can be run with `npm test`: https://github.com/CartoDB/torque/commit/86dd178abb9e85cf8d8884b1f087cec197e5e09d and https://github.com/CartoDB/torque/commit/dcd2986b9a75c0ca674d5874ee82dad6eb76fea1
* **Now it's possible to provide Canvas and Image constructor classes**: https://github.com/CartoDB/torque/commit/7499e8cf6aecac418c954f9000d8085901c42ec0
* Tests run on travis: https://github.com/CartoDB/torque/commit/40f6a4913f790fb1fb724305988c784878abf096
* Uses carto if globally present, otherwise it will use `require` to use it: https://github.com/CartoDB/torque/commit/1e83584d129e3c434a2317fba52c911c9811a8ca
* **Moves from canvas properties to cartocss properties**: https://github.com/CartoDB/torque/commit/4f251cd8cc43dcfdba0d4a994ae408856f69d34f
* The published scripts under `dist` directory will behave exactly as they do now:
  * `torque.uncompressed.js`: will require to have `carto` globally accesible
  * `torque.js`: uglified version of `torque.uncompressed.js`
  * `torque.full.js`: uglified version with `carto` library bundled