Use device detector to filter bots

[tacataca]

Change the bot filtering system to use the device detector gem.

Very straightforward swap to use a much better maintained list, however introduces an external dependancy. Also updates the rake task.

Took the liberty to also fix some issues with the CI.

[rokumatsumoto]

Hi @johnmcaliley,

Can you or other contributors review this PR?

Thanks!

[lusinh]

@tacataca You should resolve conflict