Added editorconfig and rubocop gem

## Changes 

### Editorconfig
* Added .editorconfig file, you can find more information here: http://editorconfig.org/

### Rubocop
* Added rubocop gem and updated code to conform to rubocop standards - please note however that I have not fixed all issues, please see the link below to view the configuration settings: 

https://github.com/jonathanchrisp/site_prism/blob/rubocop/.rubocop.yml 

These could be removed and the offending code fix as and when. To see more information about Rubocop please see: https://github.com/bbatsov/rubocop

* Please note that I added rubocop to the .travis.yml file, this runs before rake.

I've ensured that all units tests passed locally as expected. This appears to be a large change but the majority of the changes are small updates, such as removed "" in favour of '' etc.