Switch to grunt-bump in order to keep bower.json in sync

The version in `bower.json` doesn't get updated by grunt-release so I got this warning when installing:
```
bower wyrm#*    mismatch Version declared in the json (0.0.2) is different than the resolved one (0.0.174)
```

I swapped grunt-release out for grunt-bump because it allows you to specify multiple files to bump. I think I replicated the default configuration of grunt-release, but there might be some differences.