social toolbar tweaks

Made some minor mods to reduce noise induced by social toolbar.

Should look something like:

![image](https://cloud.githubusercontent.com/assets/1341391/4362179/132a062c-428b-11e4-96a9-cf7aecf8deef.png)

'Share this' label is no longer used and has been removed from view and style guide. 'Send this' is retained as those icons are less obvious.
This should be using `+size(18px)`