various changes to avoid code repetition and separate the module's logic from config passed to the grunt task
Merge branch 'master' of https://github.com/Financial-Times/o-ft-icons into DRYer

# Via Andrew Betts (1) and Rhys Evans (1)
* 'master' of https://github.com/Financial-Times/o-ft-icons:
  updated o-assets use

Conflicts:
	scss/_variables.scss
Merge pull request #34 from Financial-Times/DRYer

DRYer