enable limits for certain sums of rational functions
latex(): Separate numbers with \cdot by default.

Fixes issue 3740: Don't use \times in latex
http://code.google.com/p/sympy/issues/detail?id=3740
latex(): Print True/False as latex mathrm.

Also prevent IPython from printing True/False as latex at all.

Fixes issue 3757: True and False in latex
http://code.google.com/p/sympy/issues/detail?id=3757
latex(): Add empty {} argument to array printing.

Fixes issue 3861: latex(Matrix, mat_str='array') misses first element
http://code.google.com/p/sympy/issues/detail?id=3861
resolve problem of simplify_logic with Implies
Added tests
Changed Implies and Equivalent to support numbers
Rectified errors in tests
Matrix: a special technique for finding the determinant of 3x3 matrix
Fix LaTeX printing bug for Chi.
Merge pull request #2180 from seshagiriprabhu/matrix

Matrix: a special technique for finding the determinant of 3x3 matrix
Merge pull request #2175 from srjoglekar246/simplifybug

Implies and Equivalent now map numbers to (True, False)
Merge pull request #2151 from zanzibar7/limit_bug

enable limits for certain sums of rational functions
Merge pull request #2167 from jrioux/printing

LaTeX printing bug hunt
Remove e.is_Add branch in limit():

    This should fix issues, like mentioned in
    https://groups.google.com/forum/?fromgroups=#!topic/sympy/61pRw1PINUA
    or issues 2641 and 3461.
test for limit(Sum(1/x, (x, 1, y)) - 1/y, y, oo), now raises NotImplementedError
Add XFAIL test for issue 3744
Tests for issues 3461 and 2641