Don't whine when intero was manually killed

[parsonsmatt]

Sometimes I kill the Intero process in order to save memory usage. When I do so, every time I save with the Neomake maker I get an error that the Intero process is still starting up.

[kokobd]

Same issue after I quit vim accidentally. Intero no longer works for the current project even if I re-install it. It works for my other projects though.

[parsonsmatt]

To do this, it seems like we should save a flag that indicates (to the best of our knowledge) whether or not intero is "on." This state would be updated on start/stop of the intero process, and we could update it if we get any errors (eg if I kill intero manually, then try to get the type of something, it should say "Intero isn't active" and then save that information).