Improve shape evaluation.

Shapes can now be resolved for slice and reduce operations without
evaluating an expression first.
Merge branch 'master' into fix-shape

Conflicts:
	spartan/expr/reduce.py
Trying to fix travis.
Merge pull request #61 from fegin/master

Make Transpose and Reshape support foreach_tile() and tile_shape()
Merge pull request #69 from spartan-array/travis-ci

Mostly fix travis-ci build.