latex(Mul()): Deal with integer coeff.
latex(Mul()): Deal with short and long fractions.

- Print short fractions as p/q
- Print long fractions as \frac{p1}{q} (p2), where p1 is a coeff
  and p2 is e.g. an Add.
Implement and use _needs_mul_brackets.

This is used to determine if a term appearing in a Mul needs to
have surrounding brackets or not.
Some simplifications and comments.
Use mul_symbol instead of a space as separator.
Render the allowed numer/denom ratio for long fractions customizable.
fold_short_frac defaults to True for inline and False otherwise.
Let _print_Mul handle expr raised to negative powers.

Fixes issue 2576: latex(1/x**2) should return a \frac
http://code.google.com/p/sympy/issues/detail?id=2576
Add latex printing tests for fractions.
latex(Mul()): Don't special-case coeff.

Print x/2 as \frac{x}{2} instead of \frac{1}{2} x. This makes it
consistent with str and pretty printers and simplify the code
quite a bit.
Refine needs_mul_brackets.

Use expr.has() instead of isinstance to account for e.g.
Mul(2, Integral(x, x)) which needs brackets.
Changed SPDE from recursive to iterative

changed SPDE function from recursive to iterative as it is called in most of the other functions like(rischDE ,paramrischDE etc)  which on a recursive call makes it difficult to compute ouput because of recursion limit getting exceeded
replaced lines like pow_a = pow_a + 1 with pow_a += 1
Adds test case to test_rde(test_spde)

adds a test case to check *if not c.rem(g).is_zero:  # g does not divide c* raising a NonElementaryIntegralException
doctester: support comparison of floating point numbers
fix travis failures: floats with more than one leading dot are not allowed
automatically import some future imports for all doctests
float parser: support complex numbers and floats in scientific notation
unskipped several doctests
moving imports of numpy (and matplotlib/mpl_toolkits) out of module scope and into functions/classes
reduces the import time of sympy by 50-75%.

See discussion at https://code.google.com/p/sympy/issues/detail?id=3427