better Travis integration

- removed Yast stubs, install real Yast instead
- run all tests at Travis

Conflicts:
	test/helpers_spec.rb
spec_helper.rb - force loading all Ruby files

to report proper code coverage
switch to SVG badges
code style fix - use do/end for multiline blocks
use `rake test:unit` for running tests at Travis
better load all files in tests
use a shared script in .travis.yml
use the SLE-12-GA Travis script in the SLE-12-GA branch
use SLE-12-GA branches in README.md badges