Removed from assumptions/ all the extra functions, returning just True/False (issue 2152)

    Use instead AlwaysTrue/False methods, defined in CommonHandler class
Merge pull request #1973 from skirpichev/2152-rishabh

Removed from assumptions/ all the extra functions, returning just True/False (issue 2152)
Add Rishabh Dixit to the AUTHORS/aboutus. Welcome to SymPy!
Merge pull request #1974 from mrocklin/determinant

Determinant
trace/determinant(x) > 0 if x is positive_definite
_eval_rewrite and doit safe for non-Basic args
add MatrixElement
MatMul._entry simplified due to MatrixElement
diagonal elements of pos-def matrix are positive
use sympy.matrices.expressions.transpose.transpose
remove X.T -> X if X is symmetric
remove determinant of singular matrix check
refactor blockmatrix 2x2 inverse
unitary and normal predicates
add matrix fft