Better random resource retrieval

It was using a retarded approach to obtaining a random row from the database.
Now uses a SQL function. Bad thing is that it only works for PostgreSQL, SQLite
and MySQL, but I think is enough for now.
Returning strings > 36 chars
Simpler slugify

Moving slugify away from the models file, makes no sense to have it there.
Simplified algorithm, no DB hitting.
Added SQLite prerequisite
Added /whatsnew resource
/whatsnew documentation
Checking for repeated slugs after writing to DB

DERP.
Unifying output format