Fix syntax

cap aborted!
SyntaxError: /usr/local/rvm/gems/ruby-2.1.1/gems/bigpanda-0.1.2/lib/bigpanda/capistrano.rb:44: syntax error, unexpected ':', expecting =>
                            :source_system: "capistrano"
                                           ^
/usr/local/rvm/gems/ruby-2.1.1/gems/bigpanda-0.1.2/lib/bigpanda/capistrano.rb:45: syntax error, unexpected '}', expecting keyword_end
                            })
Merge pull request #3 from iMelnik/patch-1

Fix syntax