integrals: An amendment to spde()

The iterative version of spde() currently assumes that the
coefficient  a  of  Dp  were invariant in the loop, in which
case the values of the multiplier  alpha  are powers of  a.
Otherwise the offset  beta  of the solution will be incorrect.

I have added two test cases where  a  is not invariant.
In the general case,  alpha  can be used instead of a power of  a
to construct the correct value of  beta.
Don't force push to sympy_doc
Deploy the docs as part of the script phase in Travis

This has several advantages:

- If it fails, the build will fail.
- We do not need to rebuild the docs. They are already built from the test
that builds the docs.
- We do not arbitrarily only deploy when the first test in the matrix is
finished. The deploying is now tied to the docs building matrix.
Fix bash syntax in .travis.yml
Fix name of deploy script in .travis.yml
Generalize physics.quantum.OuterProduct so that it can handle scale kets/bras and sums of kets and bras
Unit tests for updated OuterProduct in the physics.quantum module
Evaluate dif for inequalities only if arguments are reals

fixes #8288
product should return 1 if term=1, fixes #8301
Fix tests
Sum evalf of non rational term
doit() keeps unevaluated Product, if _eval_product returned nan
Eval Abs(exp(x*I)) as 1 if x is real

- also rewrite re and im in terms of each other
Change version to 0.7.6-git
Add Duane Nykamp to AUTHORS/aboutus/mailmap. Welcome to SymPy!
reposition Leonid Blouvshtein in AUTHORS/aboutus
Improve handing of Abs(b**e) when b is real
fixes Abs(x)**-3 bug
Integrate functions multiplied by Heavisides

- uses manualintegrate to deal with complicated cases
Merge pull request #8214 from asmeurer/travis-docs

Travis docs