Adding a shortcut that selects the kind of comment

[Halbaroth]

First of all, thanks for your cool plugin :)

I am a lazy guy and I can't remember two shortcuts when I could use only one. I mainly use your plugin to temporary comment code blocks. To do so, I am used to hit gb in visual mode. I use some exotic languages that don't support comment block or line block, which means I have to remember which ones support comment block, otherwise the gb shortcut fails.

It would be nice to have a smart shortcut that select the appropriate kind of comment according to the file type.