Add bufferLines option to ChildProcess.exec

It ensures that stdout and stderr callbacks are triggered with whole lines

src/stdlib/child-process.coffee

@@ -8,6 +8,11 @@ module.exports =
 class ChildProccess
   @exec: (command, options={}) ->
     deferred = $.Deferred()
+
+    if options.bufferLines
+      options.stdout = @bufferLines(options.stdout) if options.stdout
+      options.stderr = @bufferLines(options.stderr) if options.stderr
+
     $native.exec command, options, (exitStatus, stdout, stdin) ->
       if error != 0
         error = new Error("Exec failed (#{exitStatus}) command '#{command}'")
@@ -18,3 +23,11 @@ class ChildProccess
 
     deferred
 
+  @bufferLines: (callback) ->
+    buffered = ""
+    (data) ->
+      buffered += data
+      lastNewlineIndex = buffered.lastIndexOf('\n')
+      if lastNewlineIndex >= 0
+        callback(buffered.substring(0, lastNewlineIndex + 1))
+        buffered = buffered.substring(lastNewlineIndex + 1)