Added LinkedIn social share option

Now have a LinkedIn page level sharing option on most content types. 

Galleries do not have a LinkedIn sharing option.

# LeftCol:
![screen shot 2014-10-30 at 11 02 50](https://cloud.githubusercontent.com/assets/2236852/4842400/f753e1b8-6024-11e4-932f-f4b983fd8f14.png)

# Mobile:
![screen shot 2014-10-30 at 11 03 12](https://cloud.githubusercontent.com/assets/2236852/4842402/017fe1b4-6025-11e4-9fe3-4a5bfde190d2.png)

# No LinkedIn on galleries:
![screen shot 2014-10-30 at 11 04 23](https://cloud.githubusercontent.com/assets/2236852/4842404/09100bb6-6025-11e4-9a2f-8fefc4ff144f.png)