cleaned up some comments
updated dealloc
[#7] catch Java exceptions on background threads

bitcoinj provides a way to set an uncaught exception handler which will
be called every time an exception is thrown in an event handler e.g.
after a blockchain change; we use this to pass the exception to the
Cocoa side
HIBitcoinManager header - comment reformatting
[#7] option to set a Java exception handler block
[#7] run the exception handler on the main thread
[#7] include Java stack trace in exception info
fixed typo (receipent)