Updated maven version
Added constructors to JSONTransferAPIClient & BCTransferAPIClient

This enables the use of java Keymanagers for authentication.
Added option to make BaseTransferAPIClient thread-safe.

By default it is not, since SSLSocketFactory does not seem to be. Also added example code (ExampleParallel) to demonstrate the issue.
Javadoc
Merge pull request #2 from makkus/master

Fix for thread-safety issue