enable airline back on close

[tap349]

enable airline back on close. otherwise it remains disabled in some cases - e.g. after invoking CtrlP.

steps to reproduce:

• call Extradite and close it
• call CtrlP and close it too

-> airline statusline is disabled (the whole statusline is blue in my case - I'm using lucius color theme).

[int3]

This seems like a problem that should be fixed in the airline code... why should this plugin have airline-specific code?

[xaizek]

Actually, 52326f6 added let w:airline_disabled = 1 for #37. Alternative would be to fire custom event(s) on close/open of extradite, so users of airline could disable/enable airline themselves. I didn't thought of this solution then.