avoid the annoying hit-return issue on messages

[svalaskevicius]

a quickfix to avoid hit-return messages in vim (neovim) when echoing messages of correct length.

disables showcmd and ruler as they are being checked here: https://github.com/neovim/neovim/blob/7795829767818a3c6cbeed7957a1ad5c03d48d41/src/nvim/option.c#L5284
once echoed, restores the state

[svalaskevicius]

alternative idea is to use a preview window.. and show full message instead of trying to cram it in the status line :) something like this: https://github.com/pushcx/ale/pull/1/files just maybe adjusting the height to the lines required too..

maybe at some point.. for now just to get those "Hit enter... " out of the way

[mlopes]

Merging this PR would mitigate the issue I described on issue #408 where the pluggin becomes completely broken (the user is asked to repeateadly press enter preventing them from editing the offending line) if the user doesn't use syntastic.

[svalaskevicius]

actually, using quickfix feels quite good, more usable than the ticker based scroller - experimenting with it in my branch - svalaskevicius/ensime-vim@ad93522

will continue testing it for time being (as that branch is quite hacky/experimental still), could make a separate PR if anyone interested? (or can add to this one)