Add log level parameter to add_rollbar_handler
Add log level parameter to add_rollbar_handler

Allows users of the helper to specify the minimum level of messages
passed to Rollbar.

RickMohr/otm-core,maurizi/otm-core,RickMohr/otm-core,RickMohr/otm-core,maurizi/otm-core,maurizi/otm-core,maurizi/otm-core,RickMohr/otm-core