Added Gitter badge
Merge pull request #244 from wagnert/master

Change Travis-CI pthreads version to 1.0.1 instead of latest beta
Merge pull request #243 from gitter-badger/gitter-badge

Add a Gitter chat badge to README.md
Replace unnecessary GenericStackable => TechDivision\Storage\GenericStackable
Merge branch 'techdivision'