Merge pull request #107 from trevorbernard/master

Fix issue with Blob hashCode and capitalize enums in zmq
Guard starting separately. Use try/finally for slot_sync
Change to not explicitly check for null

The implementation does this already
Remove superfluous comment
Use UTF-8 as default charset
Fix issue #109 - Make ZMQ.Context and ZMQ.Socket implement java.io.Closeable