Cmd* items should not be export in main.
fix issue with return code in goveralls script.

return proper code when a failure occurs in the tests.

Fixes #30
Merge pull request #33 from rochaporto/bug/goveralls#30

fix issue with return code in goveralls script.
add cli pkg, add airspace-get, added soaringweb.

adds a new cli package holding all the cli command implementations, for
now only airspace-get.

added an Airspacer interface with get/put methods, and an implementation
of the Get method for soaringweb.

adds a new plugin interface, to be implemented by all plugins.

added a mock package for dummy implementations of all interfaces (useful
for testing).