Default email address / typos

First of all thanks for developing and sharing this module. I was looking for a light-weight payment gateway solution and this module is great :) I built Fundraising module on top of PG API and found some minor issues in the process so here's a patch to rectify them:

• A personal email address is set as the default email address for notifications. However the person probably prefers not to receive error messages from different sites so it's been replaced by ini_get('sendmail_from')
• Also in arrays within hook_menu(), MENU_CALLBACK was missing a B