Fix typos in Contributing.md

`contibute` → `contribute`
`brach` → `branch`

* 'master' of github.com:shower/shower:
  chore(package): update load-grunt-tasks to version 3.4.0

load-grunt-tasks@3.4.0 untested ⚠️

http://greenkeeper.io/

index.html should not be executable

Remove moot `version` property from bower.json

Per bower/bower.json-spec@a325da3

Also their maintainer says they probably won't ever use it: http://stackoverflow.com/questions/24844901/bowers-bower-json-file-version-property

Touched up a few typos in Readme.md

Touched up a few typos in Readme.md. (Didn't add this in Issues first, because thought you might want to keep that to proper bugs and feature requests.)