Update get_blast
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
vjustov/sailthru-ruby-client,sailthru/sailthru-ruby-client,biegel/sailthru-ruby-client,HannahLehman/sailthru-ruby-client