code-completion doesn't replace expected text when cursor is not at the end of name

- VSCode Version: 1.4.0
- OS Version: Windows 10

Steps to Reproduce:
1.  Create a method called `methodOne`
2.  Write some code that calls this method as `methodTwo()`
3. Place the cursor between the `d` and `T` and invoke completion
4. Select `methodOne` from the completion list

You would expect `methodTwo` to be replaced with `methodOne` but you end up with `methodOneTwo`.
