Adding a variable to prevent a global variable leak; Removing an errant .DS_Store
slashListname leaks to the global scope.

slashListname is not defined, but is used within function block scope,
allowing it to be hoisted into the global (window) scope; causing
memory leak.
targetBlank option is being passed through as an attribute
Merge pull request #81 from sproutsocial/master

A variable was being leaked in the global (window) scope.