Fix coverage_doctest.py to work in Python 3
Fix pyflakes warnings in coverage_doctest.py
issue #2766

removed the unused prec argument from wigner_3j and clebsch_gordan
and their respective docstrings.
Cleanups: one spelling fix, three tests with XFAIL removed.
Merge pull request #2989 from Tempel/cleanups

Cleanups: one spelling fix, three tests with XFAIL removed.
Merge pull request #2985 from abhinavchanda/2766

Issue #2766 solved
Merge pull request #2951 from asmeurer/coverage_doctest_py3

Make coverage_doctest.py work in Python 3
Added Tests for wigner.racah()
Removed unnecessary import
Removed useless prec argument from clebsch_gordan and wigner_3j
Renamed test file
Small change
Fixed Travis fail issue
Added test for half integers for which racah was raising error earlier
Merge branch 'wignerfix' of https://github.com/debugger22/sympy into wignerfix