Update scenario file creation instructions in README
Added support for SIPp options other than 'optional'
Merge branch 'master' of github.com:wdrexler/sippy_cup
Better defaulting of parameters.
Update README
Added an example of multiple parameters to the README
Fix defaulting of 'optional' parameter
Correctly assigning attributes to <recv> nodes
Defaulting 'optional' to false in receive_answer not necessary
Merge pull request #3 from wdrexler/master

Allow assignment of optional parameters to SIPp tags