Modified latex printing of Lambda to use \mapsto
Modified tests so working with \mapsto version of Lambda
Removed  that I forgot about in test_latex.py
Modified tests to include parentheses around whole Lambda expression
Corrected tests for Lambda
Merge branch 'latex_Lambda' of https://github.com/dpsanders/sympy into dpsanders-latex_Lambda
Correct failing test
Merge pull request #7660 from debugger22/dpsanders-latex_Lambda

Change latex output of Lambda to use \mapsto