fixed setRoute behaviour

[merrifieldbrian]

Added splice route ability as specified in ReadMe. (#235)
Also fixed typo on line 225 where 's' is used instead of 'val'

[asazernik]

This can be squashed into one commit (since the second commit fixes a bug in the first), and I'd prefer for the check for typeof val == 'string' to only be done if the first two arguments are integers. Otherwise we'll call to splice with e.g. setRoute("some", "garbage", "arguments") and give a really unhelpful error message.

But yeah, this totally needs to be merged, especially since the documentation indicates that this behavior should already be implemented.

[merrifieldbrian]

created new pr (#314) to squash extra commits