add $CURSOR for position in zsh.sh script

[binduwavell]

fixes #23

[mklabs]

Great! Could you update the test as well ? https://github.com/mklabs/node-tabtab/blob/master/test/complete.js#L19

We should probably add a bunch more to cover all possible cases you described in #25

I still need to improve the tests a lot more. I'd like to be able to programmatically trigger a tab completion but not sure how to do it, for now, we'll just tests stdout result.

[binduwavell]

You're existing tests pass and I only made zsh behave the same as bash, so I assumed for this commit I didn't have to write extra tests.

[mklabs]

oh, that's true :) Merging in this case.

Though I need to cover zsh too.

[mklabs]

Thanks again!