Must guaruntee a MemberExpression has been hit while traveling up the tree

If a `console` identifier is in the source without accessing any of it
members this will fail to remove it and result in a runtime error.
Also need to check here to make sure we aren't trying to access a property of an undefined variable.
Merge pull request #18 from matthewrobb/master

Must guaruntee a MemberExpression has been hit while traveling up the tree