Tests for the 'Ei(z)' function rewriting
Tests for the '_eis(z)' helper function
Add a limit of 'Ei' which was wrong before adding '_eis'
Implementation of 'Li(z)'
Test args of 'Li(z)'
Improve doc of 'Li(z)' and add differentiation and numerical evaluation
Fix review comment
Import mpmath from sympy
Add tests for the 'Li(z)' function
Cross references between the various f(z)-integral functions
Add 'Li(z)' to the docs
Fix typo
Merge branch 'master' into new-polys

Conflicts:
	sympy/integrals/tests/test_risch.py
	sympy/printing/pretty/tests/test_pretty.py
polys: Added support for <, <=, >, >= to FracElement
Note that substitution does not change the variable either
Add a basic index for the new tutorial
Add new tutorial to the main index
Fix typo
Merge branch 'master' into tutorial

Conflicts:
	doc/src/tutorial/tutorial.en.rst
Start the solvers section of the tutorial