Update get_blast

https://github.com/sailthru/sailthru-ruby-client/commit/8a7af9b1cd352fbee699b001c05a7f24eade381e

Don't want create a vars parameter when it is optional - would like to leave the door open for future optional parameters as well
Update set_email

https://github.com/sailthru/sailthru-ruby-client/commit/1e18f74f072c6e4b54420566cf95effa6673b28c

Don't want create a optout parameter when it is optional - would like to open the door for other optional parameters as well
Added change_email method

https://github.com/sailthru/sailthru-ruby-client/commit/a755fa8c588fbf0e6507d713cd8cee9dc72cd7da

I changed some of the naming conventions, added optional parameters, and removed the bug of using the parameter 'email_was'
Merge pull request #22 from sailthru/bug-5627

Bug 5627