added coverage and pep8 checks

* check pep8 with flake8
  - for now pep8 is not to break the build, but we shall fix it and switch in near future
* check the code coverage (in tox)
* upload coverage results to coveralls (from .travis.yml)
  - installed and run only after successful build - saves time

Note: based on https://github.com/petrblaho/python-tuskarclient/blob/master/
minor pep8 fixes

* fixed pep8 to pass, for now:
  - max-line 90 two issues are ignored until decided otherwise
  - disabled E701 (multiple statements on one line) and E126 (continuation line over-indented for hanging indent)
* as now pep8 passes (and is quite loose), it can be activated to change travis build status