Refactored out common helper methods
Refactored out common helper methods

 * remove all unused arguments from all methods
 * add new CronofyException class
 * check if cURL extension is loaded
 * created and used http_get, http_post, http_delete helper methods
 * add get_account method to retrieve information for the authenticated
   account
 * add get_profiles method to retrieve a list of all the authenticated
   user's calendar profiles
 * increment class version from 0.2 to 0.3

Closes #5

cronofy/cronofy-php,cronofy/cronofy-php