Randomgen

- Updated Xoroshiro120 to use AUthor's latest parameterization
- Closely synchronized with the version of randomgen being integrated
into NumPy, including removing:

- ``random_raw``, which have been moved to the individual basic RNGs
- ``random_uintegers``, which can be replaced with `randint`.

- Added `RandomState` as a clone of NumPy's RandomState.
- Removed `LegacyGenerator` since this is nolonger needed
- Fixed many small bugs, including in cffi and ctype interfaces

This is a minor release with doc changes and a small edge-case fixed:

* Synchronized with upstream changes.
* Fixed a bug in gamma generation if the shape parameters is 0.0.

Release bug fixes and upstream changes:

- Fixed a bug that affected ``DSFMT`` when calling `jump` or `seed` that failed to reset the buffer. This resulted in up to 381 values from the previous state being used before the buffer refilled at the new state.
- Fixed bugs in `Xoshiro512StarStar` `Xorshift1024` where the fallback initialization used too few bytes. This bug is unlikely to be encountered since this path is only encountered if the system randomnumber generator fails.
- Synchronized with upstream changes.

Release with new generators, improved generation for integers and synchronized with upstream changes:

* Added Xoshiro256** and Xoshiro512**, the preferred generators of this class.
* Fixed bug in jump method of Random123 generators which did nto specify a default value.
* Added support for generating bounded uniform integers using Lemire's method.
* Synchronized with upstream changes, which requires moving the minimum supported NumPy to 1.13.

Release the brings in upstream changes and syncs version numbering with NumPy.

There have been no changes to the core features or supported basic RNGs.

Small release that fixes import noise on legacy Python:

* Add absolute_import to remove import noise
* Spelling corrections