Added post excerpt function, seems to work perfect so far.

This is a new setting and if one isn't set or is not a proper numeral a default is used. Update, I have added a little message to the end of the excerpt if there is actually more to the post. This post should not being showing the message cause it hasn't reached my word setting. I am pretty excited to be adding a admin page to enable/disable a few of these new custom settings, right now they have to be edited using a config file section. Not a big deal but requires the use ftp.