Return non-zero for bad or insufficient parameters
Merge pull request #696 from gasull/exit-status-ubuntu-installer

Return non-zero for bad or insufficient parameters
Deactivate bad unused import.

* ebaysdk missing from project requirements.
Enable pylint imports check (F0401).
Do not pylint inside html/bower_components.
Subpackage db and test folders.

* Effectively allows relative imports from/to these folders.
Fix broken imports in the db, features and test packages.
Locally disable import errors.

* Unable to import distutils.utils in Travis CI.
Remove line in travis to find out if build passes
Merge pull request #697 from gasull/wip-rm-line-travis

Remove line in travis to find out if build passes
Merge pull request #665 from Renelvon/sane_imports

Install package structure. Fix imports (part 1). Enable pylint flag F0401.
Factor GUID definition in a new file.

* Abstract initialization of AbstractGUID inside
  initialization of CryptoPeerConnection
* Coerce string to AbstractGUID when adding contact.
Support unicode GUIDs.
Test AbstractGUID.

* Also test CryptoPeerConnection subclassing.
Update documentation.
Replace authorship with a docstring.