Pull request for generating html documentation

I need to add two attributes to the WashOut::Param in order to be able to use this to generate documentation 
and two new options for WashOut::Soap to specify a description for each action and a list with possible exceptions that the method can raise.  

( This is as a result of this pull request https://github.com/inossidabile/wash_out/pull/125 )
( this feature is made in another gem that is going to be dependent on this gem, not yet published )