Remove space from file names

[xander-zitara]

The space introduced with the addition of the spare kernels directory breaks Rust builds in Bazel (which doesn't like spaces!) for any project depending transitively on matrixmultiply. I have replaced the space in spare kernels (making it spare_kernels) to fix this problem, and confirmed that this crate builds and tests pass.

Fixes #79

[bluss]

Do you know why a modern tool has such strange restrictions, and who uses Bazel?

[xander-zitara]

Do you know why a modern tool has such strange restrictions, and who uses Bazel?

Bazel is somewhat common for large projects that use multiple languages (imagine some code base with any combination of Rust, C++, Go, Java) in my experience. I don't know the reason for the restriction.

[bluss]

Thanks. I'll squash merge this to clean up the history. And make a note that Bazel is quirky.

v 0.3.7 released