Remove unused dependency "mime-types"

[nj]

mime-types is not referenced in the code, making it unused.

Was originally introduced through eventfuel#4.

Have cherry-picked from #251, which most likely was closed due to build failure. Without the lock that also was introduced in that PR, everything seems to go as expected - so Travis is happy 😉

[piya23300]

I have a problem.

Bundler could not find compatible versions for gem "mime-types":
  In snapshot (Gemfile.lock):
    mime-types (= 3.1)

  In Gemfile:
    carrierwave_backgrounder was resolved to 0.4.2, which depends on
      mime-types (~> 2.99)

    google-api-client (~> 0.11) was resolved to 0.19.8, which depends on
      mime-types (~> 3.0)

Running `bundle update` will rebuild your snapshot from scratch, using only
the gems in your Gemfile, which may resolve the conflict.

I think this MR can fix it.

[nj]

@piya23300 Yeah, but sadly it seems like the gem isn't maintained any longer 😢 Been over a year since last change.

What you could do though, is reference my branch or pick one of the many other forks that have handled the issue, so you're not "blocked" from upgrading.

[piya23300]

@nj this gem is live or not? it has many PRs but gem owner doesn't response.

I have problems

• dependency 'mime-types'
• recreate_versions! doesn't enqueue a job .recreate_versions! and .recreate_versions!(:version) doesn't work. But correctly work without carrierwave_backgrounder #164

Can you suggest a good fork?

[lardawge]

Fixed in master