Release: don't build Python 3 tarball

Just build one tar.gz, it should work with all Pythons.
Document the logx parameter in Expr.nseries()

Add doctests. This parameter was introduced in
9c46974da12df56818020e29f76313fc0903ecc6 but it was never documented.
Docs updated
Intro and module structure completed.
Fix heuristics for real, bounded symbols, for example: limit(r*sin(1/r), r, 0)
More cleanup in heuristics()
Fix fact extraction from composite assumptions.

_extract_facts is only passed expressions in CNF and returns None
when it can't find a meaningful fact to extract.

This is enough to guarantee a correct handling of all possible forms of
assumptions and allows the following to work correctly:

    assert ask(Q.real(x), Q.real(x) & Q.real(y)) is True
    assert ask(Q.real(x), Q.real(x) | Q.real(y)) is None
    assert ask(Q.real(x), ~(Q.real(x) >> Q.real(y))) is True
Fix tests for composite assumptions, add new ones in test_assumptions_2.py/test_query.py
Fix typo
Finished the tutorial
Fixed a typo
Fixed a typo
Fixed a doctest
Fixed Sphinx errors
Fixed the Docs
Few typos fixed
Matrix equation updated
Docs moved to Sphinx
Call simplify() in Add._eval_as_leading_term.  Fix issue 3265.
Extract nested Order expr