Makefile now creates directories needed for capabilities.py
first pass at lean projections
Changes to tests, removing coverage on one line in compute/numpy.py
Cleaned up test_compute_up_projection and field.
lean optimize summary and by-of-summary
docstring for _lean
lean optimize on sort
_lean(Symbol) doesn't project if not necessary

Thanks @mwiebe for bringing this up
sort __str__
fix docstring for lean_projection
swap_resources_into_scope function
head.str
subterms on object yields object
Switch order of args in Apply
introduce empty optimize function
test for optimize
py26 compatibility

dict comprehension -> dict((, ), ...)
remove debug print code
Reverted to old sort function, removed test.
lean optimize on head