Fixed typos
Merge pull request #3 from pborreli/patch-1

Fixed typos
generated readme with fixed typos
Added static helpers ::today(), ::tomorrow(), ::yesterday()
Updated readme for today/tomorrow/yesterday
Simplified now()
Added history file
implement __isset
Updated readme to add a small __isset section.
Simplified tomorrow()/yesterday() to rely on today()... more DRY
Simplified __set() and fixed exception text
Updated history file and added history section to readme
Added day of the week modifier methods. Including firstOfMonth(), lastOfMonth(), nthOfMonth(), next(), last(), and so on.
Fixed up spacing issues. Moved day of week names and associated them with day of week consts.
Fixed up comments and reversed parameter order on nth methods ($nth is not optional).
Fixed up comments and made the $dayOfWeek required for nth methods.
Removed trailing parameter.
Renamed last to previous to avoid confusion between last going backwards and lastOfMonth probably going forward.  I realize people say "last tuesday" but I was initially confused so I think previous makes more sense.
Use DateTime instead of always referring to its fully qualified name
DOCBLOCKS. DOCBLOCKS EVERYWHERE.