Add len operator overloading to distarray.

__len__(self) is just an alias to real_size(self), but allows the
user to use standard Python syntax instead of an unncessary API.
Add basic arange1d and tests
Rearrange arange1d tests and comment on NumPy APIRearrange arange1d
tests and comment on NumPy API
Fix stop calculation and add arange start tests
Implement start parameter for arangeImplement start parameter for arange
Add reshape tests for arange
Remove deprecated arange1d
Update arange docstring and remove whitespace.Update arange docstring
and remove whitespace.
Refactor arange tests
Add raise_exception helper assertion to Assert
Add Assert.raise_exception to add-arangeAdd Assert.raise_exception to
add-arange
Fix Assert.raises_exception when exception raised.

Fixes behavior so that if the specified exception is caught,
`raises_exception` does not raise an AssertionError.
Extend arange: make shape optional

Ensure shape xor stop is not None, raising ValueError if both are None
or neither are None. It is not necessary for the user to give both as
arguments, so this prevents users from giving conflicting dimensions.

If it is decided later to allow both to be set to non-None values, we
could use broadcasting to fill the remaining values with the stop value.
For now though, to prevent confusion, both shape and stop cannot be
supplied.

This commit adds the related tests. It also refactors tests so that
keywords are not used if unneccessary. `arange(shape, start=1)` becomes
`arange(shape, 1).`
Update arange docs and add start, stop, step tests

Add tests for possible combinations of start, stop, and step.

If shape is not supplied, calculate a 1d shape based on start, stop, and
step.

Add documentation to arange to explain new usages.
Merge pull request #159 from rgardner/add-assert-raises-exception

Add raise_exception helper assertion to Assert
Add examples to arange docstring
Merge pull request #160 from rgardner/add-len-to-distarray

Add len operator overloading to distarray.
Split test_arange into two tests (shape and stop)

These changes address the comments in #161, namely splitting the tests
and removing the extra underscore in the main function. test_arange is
now `test_arange_shape` and `test_arange_stop`, which are the two
fundamental ways of interacting with the `arange` API.
compute_slice(idx) should be able to accept an integer.
Merge pull request #161 from rgardner/add-arange

Add arange