Fixes simplification of more than two summations
Merge pull request #8608 from shivamvats/shivam/8596

Fixes simplification of more than two summations
Added the definition of sech

Definition of csch will follow in further commits.
Added the definition of csch

Also made some corrections and changes in sech and added the inverse function
of cosh.
Created a reciprocal class and added tests

1) Put sech and csch in a ReciprocalHyperbolicFunction class
to avoid code duplication
2)Added tests in core/test_args and for some basic functions
Modified tests after resolving merge conflicts
Moved some more functions to the Reciprocal class

Moved rewrite_as_tanh and rewrite_as_coth to RecicprocalHyperbolic
class.
Fixed broken TeX and tests and merged Mathematica's translations

Also did away with redundant tests
Merge pull request #8401 from shivamvats/hyperbolic

Added sech and csch under ReciprocalHyperbolic class
Create the solveset module

The commit implements the solveset module in an attempt to
fix the problems with the current solve function. The commit
roughly follows my GSoC proposal
https://github.com/sympy/sympy/wiki/GSoC-2014-Application-Harsh-Gupta:-Solvers
and more details can be acquired through the discussion on the github pull
request https://github.com/sympy/sympy/pull/7523
correct RootOf(...) in S.Reals
Add imageset.intersect(S.Reals) method