initial commit
add a smoke test
wip: introduce a pulse_ffi library
TDDing Mainloop class
add tests for run, and free

Also inject rspec's mocks into minitest
implements Mainloop.run
re-implement list-sources with Mainloop
cosmetic changes

* put script in bin/
* fully move tests to specs
add Mainloop.api
add a Context class (easy stuff first)
implements on_state_change callback
introduce SourceInfoList class, add a helper PulseTest class
Implements SourceInfo.each

Questions:
* how to implement next ?
* how to test this ?
* how to NOT quit the loop at the end of the iteration ?