806: Implement hyper.rewrite(Sum)

This adds the function _eval_rewrite_as_Sum to the class hyper.
806: hyper.rewrite(Sum)

Change return value to Piecewise
Add tests
806: Improve code style
Merge pull request #2032 from katjasophie/806_hyper.rewrite(Sum)

Issue 806: Implement hyper.rewrite(Sum)
Update Raoul in the .mailmap file
Merge branch 'master' of github.com:sympy/sympy
Hermite quadratic version to Mack's Linear version

Have reduced the time complexity involved in the hermite reduction (method) from m^2 to m-1 by using Mack's linear version instead of the quadratic function.
Also no partial fraction decomposition of f(input function )or square-free factorization of its denominator is required decreasing the time complexity further
Merge pull request #1948 from cheatiiit/hermite

Hermite quadratic version to Mack's Linear version
Add Chetna Gupta to the AUTHORS/aboutus/.mailmap. Welcome to SymPy!
ac progress
fixes
more Analytic Combinatorics constructions
Analytic Combinatorics working for unlabelled structures (needs testing)
some tests; needs more.
test stuff
some renaming, a few more tests
skeletal AC documentation
Analytic Combinatorics documentation progress
more documentation for AC module
more documentation for analytic combinatorics