Update readme and information on capcha module page

I have just wasted an hour trying to get this to work due to such poor documentation. Captcha is a great/essential module but the current documentation leaves a lot to be desired.

It needs to be made clear that:

- the form store module need to be installed and enabled for captcha to work. (If this is the case)
- Captcha points need to be added at - admin/settings/captcha/points
- remove the false information "You will need to go to admin > access control to provide users access to captcha." from the captcha download page.

Building such a great module without writing accurate and concise documentation is like baking a cake and not bothering to put icing on it. :-)

Thanks,

Anthony