Plane class
Removed trailing spaces
Merge https://github.com/sympy/sympy into plane
Changed the are_perpendicular and is_parallel method
Refactor code in projection_line method
XFAIL the test in test_args
Removed the XFAIL
Added Dummies and used free_symbols() instead of is_constant()
changed Dummy() to Dummy
Add tests to test_wester.py for set theory and continued fractions.

Also for symbolic continued fractions.
Removed Trailing Space error
Merge pull request #7682 from clsn/cftests

Add tests to test_wester.py for set theory and continued fractions.
Merge pull request #7667 from akshayah3/plane

Plane class
Added default hash value for zero vector
Removed unnecessary import
Merge branch 'master' of https://github.com/sympy/sympy into basicvector