Handles trailing slash when loading
Fixes bugs and renames slice_len to slice_shape

Renames utils.slice_len to utils.slice_shape

Addresses integer math corner-case resulting in inaccurate lengths in certain cases (i.e. slice(4,9,4) should have length 2)

Adds check to utils.slice_shape and utils.fix_slice to allow 'shape' to be an int
Removes slice.stop > size error in utils.fix_slice

Comments out error case where slice_.stop > size - this is more along the lines of how numpy functions (a slice can 'stop' at an index greater than the size of the array)

Updates tests
Merge pull request #15 from blazetopher/slice_utils_fixes

Slice utils fixes