MAINT: avoid DeprecationWarnings with numpy 1.7 in stats tests
MAINT: remove kolmogorov_check, duplicated test

* kolmogorov_check is not run, superseded by check_distribution
* remove docstrings from tests
* remove one of the two copies of check_edge_support
TST: collect entropy tests together
MAINT: collect the moments tests together
TST: collect together the tests for support edges & out-of-bounds
TST: reenable test for _ppf not NaN

and move it to test_continuous_basic
MAINT: move regression from test_continuous_extra

remove test_continuous_extra as it does not contain anything useful
anymore