Squashed 'scalyr_agent/third_party/pymysql/' content from commit 36d6b5f

git-subtree-dir: scalyr_agent/third_party/pymysql
git-subtree-split: 36d6b5f082d6d77ec05c00c56bb86d780571ceeb
Merge commit '35254fcbe6fa2d9731df6550d1ba061e2d34be81' as 'scalyr_agent/third_party/pymysql'
Added forked version of tcollector.
Added external library readme.