evaluate Pauli matrices product
fixes paulialgebra whitespaces
pauli algebra fix product
pauli algebra doc spelling fix
Add Abs.rewrite(Heaviside)
Fix error message from subs
Addtional docstrings in the differential geometry module.

Doctests were slightly updated. Explicit mention about the effect of different
coordinate system choices was added.
Work on itegral curves in the differential geometry module.

Two new functions were added to the differential geometry module that deal with
integral curves. Tests for these functions are supplied.

Integral curves are inherently represented in coordinate dependent way because
there is no coordinate independent way to present movement from point to point
on a general manifold (i.e. there is no such thing as difference between two
points).

The first function is `intcurve_series`. It produces the series expantion of an
integral curve when given the starting point and the coordinate system in which
it must work.

Specify a starting point and a vector field:
>>> start_point = R2_r.point([x, y])
>>> vector_field = R2_r.d_dx

Calculate the series:
>>> series = intcurve_series(vector_field, t, start_point, n=3)
>>> series[0]
[x]
[y]
>>> series[1]
[t]
[0]
>>> series[2]
[0]
[0]

The second function is `intcurve_diffequ` that works in the same way as the
first one, however it returns a system of differential equations describing the
integral curve.

Specify a starting point and a vector field:
>>> start_point = R2_r.point([1, 0])
>>> vector_field = -R2.y*R2.d_dx + R2.x*R2.d_dy

Get the equation:
>>> equations, init_cond = intcurve_diffequ(vector_field, t, start_point)
>>> equations
[f_1(t) + Derivative(f_0(t), t), -f_0(t) + Derivative(f_1(t), t)]
>>> init_cond
[f_0(0) - 1, f_1(0)]
Abs.rewrite(Heaviside) only happens if the argument is real
Merge branch 'master' into abs_heaviside

Conflicts:
	sympy/functions/elementary/tests/test_complexes.py
added FunctionMatrix object

This is the SparseMatrix equivalent in the MatExpr family
Edits for docstrings of FunctionMatrix
added test_args test for FunctionMatrix
bin/use2to3: Handle extension-less files correctly

The use2to3 tool previously only considered files ending in .py or .txt
to pass to 2to3. However, scripts have no extension and weren't being
passed to 2to3. This also required a hack when fixing the shebang lines.
Handle this by making a list of relevant files with no extension and
checking if the modified file is in it.
bin/use2to3: Use git ls-files

Currently, the script traverses the whole source and grabs all .py
files, skipping a few specific directories. If the user has some extra
Python files around they might crash 2to3; also, all files will be
copied to a new directory and this is not optimal. Instead, use
"git ls-files" to get a list of all the files tracked by git and only
copy those. The "old" way is removed.

Fixes issue 2673. Note that this approach is not faster than the old
one.
give a suggestion of how to fix use2to3
Better checks for Vectors, Dyadics in mechanics

The code for checking if an input was a vector or dyadic needed to be improved,
as 0's were "slipping by" sometimes. Also, consistently returns 0-vectors
rather than 0's from operations.
	Basic groups, orbit calculations, direct product, minor fixes

	Fixed the issues pointed out in the pull request discussion.

	Implemented constructors for symmetric, cyclic, dihedral and
	alternating groups as permutation groups, setting their
	basic properties.

	Replaced some of the orbit/stabilizer functionality present -
	the functions orbit, stabilizer, orbit_transversal - with faster
	implementations. Implemented Schreier vectors and
	group elements sending a given element to another element in
	its orbit.

	Implemented direct products for permutation groups.

	Made minor fixes in the docstrings and removed some duplicate
	functionality from permutations.py.
Minor spelling fix.
Merge pull request #1316 from Krastanov/vector_analysis_2

Vector analysis 2