Fix dashboard breakage
Merge pull request #853 from ghost1227/master

Dashboard widget breaks dashboard
Serialize form for AJAX request

Serialize the form instead of posting only EDD inputs. Allows for posting of custom fields via AJAX.
Fix syntax error

Replace comma with ;
Introduced edd_get_lowest_price_option(). #727
Introduced edd_get_highest_price_option(). #727
Introduced edd_price_range(). #727
Show price range in download wp list table. #727
Make sure blank prices aren't taken into consideration when finding range. #727