resize gap

[taiyu-len]

resize gaps for workspace, views via the following commands.
gaps inner|outer all|current|workspace set|plus|minus nnn
one difference in the inner current|workspace
airbladers inner current changes all view gaps for a workspace, while this sets it for the focused view.
and newly added inner workspace changes all view gaps for a workspace.

i could change inner workspace to inner view so the inner current is the same as airbladers, but it was a bit neater this way.

[ddevault]

Airblader gaps has a different syntax:

https://github.com/Airblader/i3#gaps

[taiyu-len]

ok done.

[ddevault]

Update the man page. Looks good otherwise.