do not insert duplicate values to global
fix MemberExpression assignment to unknow object
change context of FunctionExpression if it's a method
treat params as free variables, fix false positive
fix callback, they are also inside CallExpression but are not IIFE
abstract getVar logic
top level FunctionDeclaration should be considered a global
make sure window & document are considered as globals if they are not defined
fix MemberExpression if property is a Literal + tests
windows friendly `npm test`.

mocha supports globs, no need for find.
Merge pull request #2 from millermedeiros/master

fix some edge cases related to function params and methods that references `this`