Incorrect scope used for some mappings

[lifecrisis]

Greetings:

I found an interesting class of NERDTree bugs this week. It's funny, I had been frustrated when encountering these bugs before, but I could never reproduce them, so they lingered. I finally got to the source today.

To get all of the details with an example of how to fix, see the commit message here.

I would submit a PR, but my "stable" NERDTree version lags significantly behind the main line developed here. I've been using my fork because I didn't want anything to change... I found myself too comfortable with what I had. Eventually, I'll need to return to using this repository to get some of the nice, new features. ;)

In any case, this class of bugs seems to be present in this version. I thought I would note it for the benefit of all here.

Best,
lifecrisis