Rename gemspec.
Rename 'kosmos' to 'kmc' in directory names.
Rename references to "Kosmos" to "KMC".

In code, things were changed to "Kmc", but in writing they were changed to
"KMC".
Update the README to reflect the new name.
Merge pull request #409 from kmc/rename-to-kmc

Rename to kmc