refreshing dependencies

• replaced support of coverage 3 with support of coverage 4
• added support of pytest 2.8
• added support of python 3.5

v0.4

run_variants configuration option changed to run_variant_expression . Now it's a single python expression, multiple lines are not allowed. If you need a composition of many values, do it in the python expression.
Also the format of .testmondata changed so plese remove the file and have it recreated.