Combinatoric Cheatsheet

A combinatoric cheatsheet. It include methods names and a short
description.
Modified latex printing of Lambda to use \mapsto
Modified tests so working with \mapsto version of Lambda
Removed  that I forgot about in test_latex.py
Modified tests to include parentheses around whole Lambda expression
Corrected tests for Lambda
Floats - neither rational nor irrational

A Float represents an interval of real numbers, both rational
and irrational. It cannot be meaningfully tested for rationality.
Merge branch 'master' of https://github.com/Mba7eth/sympy into comb_cheat
Updated Makefile for combinatoric cheatsheet.
Replaced 'interval' with less exact expression.
Started work on Linearizer Class

Implemented routine for constraints on position and velocity.
Unsure if it will work if either are missing, most likely will need
to add control flow for this. The API is also complicated, and will
be simplified as more code is ported over.

Also added one test for the new linearize routine. Based off of
the example in Luke and Gilbert's paper. As more functionality is
added to the linearization routine, the work done in this test
will get smaller. Still need to add more tests from the examples
I worked out last week.
Fix latex subscript, etc use in ode.py lines 3671-2

Fixes #7417
Made some edits of latex and edited desription of ode_1st_power_series doc

More Fixes for #7417
Lots of work on linearization methods

- Added `to_linearizer` method to KanesMethod class. This returns
an instance of Linearizer with all information needed for the class.

- Made 1 meaninful test with the rolling disc test case. The other
two tests aren't finished yet.

- _subs_keep_derivs was written. This substitutes in values for symbols,
but keeps the derivatives of the from being substituted out.
Whitespace removed in ode.py
Modified func_coef
Added first method for linear system 2nd order 2eqs
Fix too long line.

On line 2782 in ode.py there was a too long line. I separated the line into two
Added first method for linear system 2nd order 2eqs
Added method to solve type2 of 2nd order