databases/rubygem-solid_cache: Add rubygem-solid_cache 1.0.6

Solid Cache is a database-backed Active Support cache store that let's you keep
a much larger cache than is typically possible with traditional memory-only
Redis or Memcached stores. This is thanks to the speed of modern SSD drives,
which make the access-time penalty of using disk vs RAM insignificant for most
caching purposes. Simply put, you're now usually better off keeping a huge cache
on disk rather than a small cache in memory.