Use Intel SDE in Travis CI

[mmcloughlin]

Since #7 was landed this package now contains architecture dependent code with a cpuid based feature check. Therefore in CI we are only testing one code path, and also not confirming the feature check is implemented correctly.

Unfortunately multi-architecture testing is very challenging. However the Intel SDE tool could allow us to emulate various intel CPUs. See flame/blis#122 and flame/blis#124 for an example.

I would like to consider using this for the geohash package. At first glance it appears the annoying part is installing SDE in travis, since the download requires you to accept a license.

[mmcloughlin]

Example:

https://github.com/mmcloughlin/meow/blob/871e50784daff1c9ec5ef66fe3d8fda6bbcd42cf/.travis.yml

[mmcloughlin]

Don't think this is important enough to work on right now. Closing as wont fix, could potentially reconsider in future.