add @each control directive & other small edits

Create new @each control directive & sass variable list to control the various social class ruleset creation.

This should make it much easier to add or remove social classes and update all classes by editing single directives.

//  other edits

from li {} selector:

remove display: block; because <li>'s are already display blocks, and the float:left also makes the element a display block.

remove duplicate height: 100%;

remove duplicative googleplus .style1, .style2, .style3.  these weren't any different than their first declaration in the cascade so they weren't actually doing anything.
Google plus icon fix. Will add to index.html after @scottaohara pull request. Will let us get rid of the extra styling for Google plus.
Merge pull request #17 from scottaohara/control_directive

add @each control directive & other small edits
Social list formatting