don't evaluate bool(Relational)
Merge remote-tracking branch 'rlamy/Relational' into relational

Conflicts:
	sympy/core/relational.py
Update the docstring of Relational.
Remove extra sorting step from tests whenever possible.
Test chebyshevt_root and chebyshevu_root with valid arguments.
Always specify the sort key when sorting.
Don't rely on the truth value of Rational.