Step name parametrization

Now step decorator supports parametrization -- via #65

And some minor fixes -- #59 , #62

Fix six dependency version

Via #58

Python 3 compat + Cancelled/Pending statuses

Via #55 and #56

Add environment handling

Thanks goes to @sergeychipiga for PR #49

1.5.1 re-release

Blame @pupssman for bad commits

Add allure.issue marker

Via #40 -- thanks goes to @aohontsev
See https://github.com/allure-framework/allure-core/wiki/Issues to see how to use that

Support allure-core 1.4.X

Via PR #37 -- thanks goes to @mavlyutov

Main change is that now Severity are not a special field but just another Label.

WARNING

This release introduces binary incompatibility in the allure.common's methods -- see changes.

Travis migration and test refactoring

First automated release -- only internal changes in test machinery and tests.