Made GA_Printer robust against exception abort.

GA_Printer is now a context handler.
If used in that way, it will clean up after itself even in the presence of exceptions.

Made all uses of GA_Printer use the "with" form.
Fix mathml tests in python 3.
Suggested fix for __int__ function of class PythonRational in order to enable it to work with large numerators/denominators.
Docs moved to Sphinx
Added issue numbers to @deprecated annotations.
Merge remote-tracking branch 'origin/master' into report-test-name-on-early-failure
fixed documentation bug as per issue #4029
Add doctest for translate function
Add tests for accents
TeX abs explicitly because MathJax does not know it
Issue and version numbers corrected.
Removed duplicate import.
integrals.transforms: Fix for issue 2486
raw docstring for doctest
Call simplify() in Add._eval_as_leading_term.  Fix issue 3265.
Extract nested Order expr
Handle NotImplementedError in Pow.nseries
Add test for issue 3400
Evaluate more terms for Laurent power series.  Fix issue 2555.
Add test for issue 2555