liealgebras_1: some updates
docstring for conditioning on random symbol
expand failed uniform test
liealgebras_2: Type B
Add additional tests for Derivative subs method.
Travis: don't install all the *-doc packages

This should significantly improve download time / traffic.
polys: implement modular GCD algorithm for univariate integer polynomials
polys: add tests for modgcd_univariate()
polys: implement modular GCD algorithm for bivariate integer polynomials
polys: add tests for modgcd_bivariate()
polys: implement modular GCD algorithm for multivariate integer polynomials
polys: add tests for modgcd_bivariate()
Merge branch 'master' into modgcd

Conflicts:
	sympy/polys/polyerrors.py
liealgebras_2: some updates
liealgebras_1: more fixes
Merge branch 'master' into travis

Conflicts:
	.travis.yml
Travis: fix the missing "lmroman10" problem

I followed the advice from:

http://tex.stackexchange.com/questions/652/xetex-not-working-on-ubuntu-10-04
Rewrite atan2 as arg function
Improve rewrite of atan2 in terms of arg
Test rewrite to arg