Added a few rules for imageset simplification
Implement __ne__() by calling __eq__()

The __ne__() operator should return "not __eq__()". Alternatively, one can copy
& paste the algorithm from __eq__() and negate the answer right before each
return. But anything else means there is a potential bug.
Merge pull request #7645 from certik/ne

Implement __ne__() by calling __eq__()
Added Ambar Mehrotra to the AUTHORS/aboutus. Welcome to SymPy
Merge pull request #7625 from hargup/imageset_simplification

Added a few rules for imageset simplification