Added reCAPTCHA for comments and registration

Due to an overwhelming amount of comment spam, I have added reCAPTCHA to the comments and registration process. I was dealing with 50+ spam comments for moderation per week, which is more than I am willing to deal with. Sorry for any inconvenience you may experience as a result. Once you are registered and logged in you will no longer need to submit the re-captcha for each comment, so it should be a one-time thing.