msgpack-python dependency stops use on google app engine.

[obmarg]

Some python hosting services (such as google app engine) don't allow the use of compiled python extensions. msgpack-python is a compiled python extension, so having it as a dependency is preventing me from using transit.

Could msgpack support in transit-python be made optional somehow?

[benkamphaus]

Hi @obmarg -- we're considering this. Thanks for bringing it up.

[jszakmeister]

I'd really like to see the msgpack dependency be optional as well.