Removed unique constraint on account name

Per https://assemblymade.com/support-foo/wips/63 a slug is being added
which is the identifier for the account.  It'll be URL-safe and unique
across the app.

Therefore I propose the "name" attribute is repurposed simply as the
"display name" of the account.  It therefore should not be unique.
Added a user to the seeds file
Add account slugs

Per https://assemblymade.com/support-foo/wips/63
Merge pull request #14 from drewblas/add_account_slug

Add account slug