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
Implementation of the second heuristic

The second heuristic is a method to find the infinitesimals xi and eta of
the PDE mentioned in the documentation under infinitesimals

There are four assumptions to xi and eta

1. eta = 0, xi = f(x)*g(y)
2. eta = 0, xi = g(x)*f(y)
3. xi = 0, eta = f(y)*g(x)
4. xi = 0, eta = f(x)*g(y)

g is a function got by extracting factors from the numerator and denominator
f is the function got by solving the auxilliary ODE obtained after
substituting g in the PDE. For now, it is assumed f can be obtained if
the auxilliary ode obtained is separable in f
3722: more advanced re/im support
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)
Added Seshagiri Prabhu to AUTHORS/aboutus. Welcome to SymPy!
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
rework real/imag processing; remove dup symbols
Merge pull request #2183 from smichr/auth

Added Seshagiri Prabhu to AUTHORS/aboutus. Welcome to SymPy!
Merge pull request #2178 from smichr/solve

3722: more advanced re/im support