some cleanup of standard files; added model methods to expire and unexpire account

added back require device_account_expireable

added back everything in device_account_expireable

added back require device_account_expireable

Revert "added back require device_account_expireable"

This reverts commit 46b5e5734e11ef1b901ea9aac88be33fbb5c93ef.

Revert "added back everything in device_account_expireable"

This reverts commit 926504bf4bcf6610806e4811599e5c46d319cf0d.

Revert "added back require device_account_expireable"

This reverts commit 93ea21e403390f577cd7412e75a9ea6aecccdf21.

changed expires_at to attr

add save
add self

remove save
added ! methods to save model state to db
refactored ! methods
Merge branch 'master' of https://github.com/brendte/devise_account_expireable