first draft of thread based implementation to make the code public

[barollet]

Summary of changes

This is my implementation for this issue https://github.com/cs01/pygdbmi/issues/41, it changes the way the IOManager communicates with GDB. The Controller interface is also changed and we need to discuss what will the new interface be before merging the code.

Test plan

This is only a draft I use locally, when the interface is ready I can start adding a test and do a proper pull request that can be merged.