Added function normal_lines to ellipse.py
remove dead comment/code
give normal_lines a numerical option

Also, all solutions have to be checked since if None is
returned in checksol for a test of assumptions, e.g. that
a solution is real, then that solution will be returned.
We don't want that here so we check the numerical value
but keep the symbolic one (unless prec is given).
raise Line error only in LinearEntity
do simplification only when necessary in Point
use dydx to get slope

The slope formula is based on the given point and the point on the
ellipse; but if a point is on the ellipse then that formula cannot
be used to compute the slope: the dydx form should be used.
Added Akshay to AUTHORS/aboutus. Welcome to SymPy!
Better docs for Wild, improved tests for excluded
expanded docs, as suggested
revisions for @smichr

- restore matching tests but without exclude options
- fix ,'s
- docstring revisions so doctest passes
simplify only Floats in Point.__new__
restrict multiplicative extraction of negative sign
Merge pull request #2828 from smichr/ellipse

Ellipse
Merge pull request #2831 from smichr/3973

restrict multiplicative extraction of negative sign
Fix a typo
Merge pull request #2836 from thilinarmtb/fix_docstring_typo

Fix a typo
requested changes
Added inverses to error functions.

As discussed at
https://groups.google.com/forum/#!topic/sympy/jmV52ve9Cqg
Added tests.
Removed possibly incorrect inverses