compatibility with vim-airline

[AlainPilon]

When using Extradite with Vim Airline (https://github.com/bling/vim-airline), the setlocal statusline= does not seem to work.

Instead of getting the expected timestamp of the commit, I am getting a [No Name][-] string.

Since I can manually set the status line while browsing via Extradite, I have a feeling the issue is on this side instead of Vim Airline.

[xaizek]

vim-airline sets 'statusline' on window change. Try pressing Ctrl-W Ctrl-W several times after :Extradite, I see correct status line for a while, then (after key press) it's reset.

Added setting w:airline_disabled, which seem to fix the issue.