Merge pull request #142 from lukeolson/master

consistency
Added a nonzero diagonal to classical strength measure, had to
change direct interpolation and splitting as well to handle
strength matrices with a nonzero diagonal.
Added a nonzero diagonal to the symmetric strength measure and changed
the unit tests
Added a unit test for remove_diagonal, and added text about the
desired standard strength interface
Unified the strength of connection returns for classical,
symmetric, and distance
Unified the strength of connection return values for evolution measure,
and algebraic distances.  Also, added support for all the strength
measrues in classical.
One more change to make evolution measure work with classical.py
Updated todo list to reflect work done on strength of connection
Removed old, unused commented out code at the bottom of
smoothed_aggregation.h
Fixed the documentation of UnAml in utils.py
Removed the redundant blocksize and nPDEs functions in aggregation.py
and rootnode.py
Blocked out code sections in classical.py so that they resemble
the code chunks in the aggregation solvers
Fixed issuea #95 concerning assume_constant_nns in evolution strength
Cleaned up the classical interface to evolution strength measure
Merge branch 'master' of https://github.com/pyamg/pyamg

Conflicts:
	pyamg/strength.py