fixed bug where reward image url could not be blank
Merge pull request #175 from Crowdtilt/allow_blank_reward_image_url

Allow reward image url to be blank
Refactor model error message display
added option to collect shipping for only specific rewards
renamed collect_shipping to collect_shipping_flag on campaigns
catch unsaved changes for checkbox values
Merge pull request #177 from Crowdtilt/refactor_model_error_display

Refactor model error message display
Merge pull request #172 from Crowdtilt/reward_shipping_toggle

Added option to collect shipping for only specific rewards
Pulling the most up to date version of Crowdhoster.

Merge branch 'master' of https://github.com/Crowdtilt/Crowdhoster
Moved the Mavericks issue to the dependencies section of the readme.