risch: factor out common expression.
risch: Fix WrongResult for x*exp(-k*x).

Fix issue 3886: Incorrect Piecewise result from risch_integrate
http://code.google.com/p/sympy/issues/detail?id=3886
Merge pull request #2170 from jrioux/integrals

Fix WrongResult for risch_integrate(x*exp(-k*x), x)
Add Ramana Venkata to the AUTHORS/aboutus. Welcome to SymPy!
2695: Pretty print of -x/y

Implemented one possible solution: Shift denominator one character
to the right when certain conditions apply:
- Numerator is negative,
- Numerator is even width,
- Numerator is wider than denominator.
Merge branch '2695_pretty_print_fractions' of github.com:nelsoner193/sympy into 2695_pretty_print_fractions

Getting everything to play nicely together, while making sure my branch
is updated.