Add degree_offset option to heurisch(), for testing diff degree bounds

See issue 2606

Conflicts:
	sympy/integrals/heurisch.py
Fix a logically incorrect example in the expand() docstring

The docstring was supposed to describe how to disable the log hint, which is
applied before the mul hint, but it instead showed how to disable the mul
hint, which does nothing in this case.
Expanding doc for partial fraction decomposition
gitignore: add *.c and *.so which are gen. by 'make'

Signed-off-by: Thomas Hisch <t.hisch@gmail.com>
Added matrix representation
Added to authors
Added matrix_zeros tests
Add vector representation to SHOBra and SHOKet, fixed tests, adjusted matrix_zeros in matrixutils.py
Fixed imports
Fixed doctests and import errors
Added dtype and changed default scipy matrix to lil_matrix
Fixed code quality
Merge pull request #1775 from thisch/gitignore-polys

gitignore: add *.c and *.so which are gen. by 'make'
Merge pull request #1729 from ottersmh/1dshorep

1dshorep
Add Stefen Yin, Thomas Hisch, and Matthew Hoff to the AUTHORS/aboutus/.mailmap

Welcome to SymPy!
set full=True in the example
add examples show the difference between with and without setting full=True
delete a useless example
minimize strategy
treeseach