Add support for job control

This commit adds support for job control (running processes
asynchronously from plugins) with the JobStart, JobSend, and JobStop
functions (copying neovim's job control).

This commit also makes the linter plugin work asynchronously, so the
editor won't be frozen while the linter checks your code for errors.

cmd/micro/micro.go

@@ -52,6 +52,9 @@ var (
 	// This is the currently open tab
 	// It's just an index to the tab in the tabs array
 	curTab int
+
+	jobs   chan JobFunction
+	events chan tcell.Event
 )
 
 // LoadInput loads the file input for the editor
@@ -245,14 +248,33 @@ func main() {
 	L.SetGlobal("MakeCommand", luar.New(L, MakeCommand))
 	L.SetGlobal("CurView", luar.New(L, CurView))
 
+	L.SetGlobal("JobStart", luar.New(L, JobStart))
+	L.SetGlobal("JobSend", luar.New(L, JobSend))
+	L.SetGlobal("JobStop", luar.New(L, JobStop))
+
 	LoadPlugins()
 
+	jobs = make(chan JobFunction, 100)
+	events = make(chan tcell.Event)
+
+	go func() {
+		for {
+			events <- screen.PollEvent()
+		}
+	}()
+
 	for {
 		// Display everything
 		RedrawAll()
 
-		// Wait for the user's action
-		event := screen.PollEvent()
+		var event tcell.Event
+		select {
+		case f := <-jobs:
+			f.function(f.output, f.args...)
+			continue
+		case event = <-events:
+		}
+
 		if TabbarHandleMouseEvent(event) {
 			continue
 		}