Initial Streaming API

Error checking in this release was consolidated. Debugging capability has suffered as a result, but I plan to revamp this in the future.

Added the is_available function to showcase look ahead in a streaming scenario. Added a demo showcasing this capability alongside unpack_buf. It is a start, but more work needs to be done here.

v0.3.0

Bugfixes:

• negative fix int encoding

API

• mp_float_type constructor now exposed as same name as type
• container format types now also accept regular integers as length arguments
• error messages are stored to msgpack as error_message