Use update_columns instead of save! for performance

[JasonBarnabe]

update_columns skips callbacks, validations, and transactions. It "is the fastest way to update attributes".

On a local postgres table with 40000 rows, batch size 1000, anonymizing a single email field.

Before changes: 2m 52s
After changes: 1m 32s (46% faster!)

[coveralls]

Coverage increased (+0.003%) to 93.797% when pulling 7082127 on kickbooster:update_columns into db4f509 on sunitparekh:master.

[coveralls]

Coverage increased (+0.003%) to 93.797% when pulling 7082127 on kickbooster:update_columns into db4f509 on sunitparekh:master.

[coveralls]

Coverage increased (+0.003%) to 93.797% when pulling 7082127 on kickbooster:update_columns into db4f509 on sunitparekh:master.

[sunitparekh]

Merged. Thanks for contribution. Will publish next version soon.

[krainboltgreene]

Woo!