Added DFT matrix
Change the name of function
Add support for Equivalent with multiple arguments
Fixed python3 compatibility issues
Minor change
PEP8 Style
import xrange from sympy core
Fix #7206: Equality with matrices.

Equality was changed to support objects with an _eval_Eq method.  This allows
objects to define alternative algorithms for determining equality.  Such a
method was implemented in ImmutableMatrix.
Merge pull request #7278 from debugger22/dft_matrix

Added DFT matrix in physics matrices
Merge pull request #7281 from Tempel/7206_matrix_eq

Fix #7206: Equality with matrices.
Merge pull request #2869 from SDB1323/Equivalent

Added support for Equivalent with multiple arguments in functions
Add early exit in the limit heuristics() for "bad" results with oo

    This does limit calculations in this method more
    fragle, which is good.  An example:
    >>> O(sin(1/x**2).contains(O(cos(1/x**2)))
    True
    was wrong, just because of this limit:
    >>> limit(sin(1/x**2)/cos(1/x**2), x, 0)
    sin(oo)/cos(oo)