The `latest` build remains as is, but all others are modified to:
* Use regular Python instead of conda. `pip install` is much faster
than conda, but scipy isn't available. Numpy is still tested.
* Compile in debug mode instead of release.
* Skip CMake build tests. For some reason, CMake configuration is very
slow on AppVeyor and these tests are almost entirely CMake.
The changes reduce build time to about 1/3 of the original. The `latest`
config still covers scipy, release mode and the CMake build tests, so
the others don't need to.
