Adding PTC

added logo
refactored some logic in _sponsors.txt
Merge pull request #676 from littleidea/pittsburgh

Adding PTC
fix silly icon border
Merge pull request #677 from littleidea/pittsburgh

fix silly icon border
change sponsor levels silicon valley
Merge pull request #678 from littleidea/siliconvalley

change sponsor levels silicon valley
change wording for website and color for sponsor matrix
Merge pull request #679 from littleidea/siliconvalley

change wording for website and color for sponsor matrix
india-2013 presentation list updated with Youtube talk video link
Merge pull request #680 from abhishekkr/india-2013

india-2013 presentation list updated
ams 2014 updates
added sponsor doc
Merge pull request #681 from awolfs/master

amsterdam updates
more ams updates
date fixed
Merge pull request #682 from awolfs/master

more ams updates
New Iron sponsor for Austin 2014
removing lanyard sponsor paypal button for Austin 2014
Retailmenot silver sponsor for Austin 2014
Adding the Nairobi 2014 event