3693: combsimp adjustment for ratios
fix failing tests (confirmed equivalence numerically)
allow for iteration in rule_gamma
ExpBase.as_numer_denom synched with Pow

With this change, we no longer need to look for 1/(g-1) in numer nor
1/g in denom.
tidy up bsplines
make sure bottom_up goes all the way to the bottom
refactor use of bottom_up in fu

Conflicts:

	sympy/simplify/fu.py