Move debug option to env variable

The debug module does not work well with dynamic configurations. So we need to use the environment variable to set up the debug logs.

README.md

@@ -21,14 +21,19 @@ require('spawn-auto-restart')({
 });
 ```
 
+To enable logs set an environment variable like this:
+
+```shell
+DEBUG=spawn-auto-restart
+```
+
 **advanced args options**
 
 * [spawn](https://nodejs.org/api/child_process.html#child_process_child_process_spawn_command_args_options)
 * [chokidar](https://github.com/paulmillr/chokidar)
 
 ```js
 require('spawn-auto-restart')({
-  debug: true,
   proc: {
     command: 'executable path',
     // ... any spawn argument
@@ -50,7 +55,7 @@ Auto restarting an [electron](https://github.com/atom/electron) app in developme
 
 ![](https://www.dropbox.com/s/gxird1lr72tq56s/spawn-auto-restart.gif?raw=1)
 
-**restart.js**
+**node DEBUG=spawn-auto-restart restart.js**
 ```js
 #!/usr/bin/env node
 
@@ -63,7 +68,6 @@ var watch = join(__dirname, '../src/browser');
 
 
 require('spawn-auto-restart')({
-  debug: true,
   proc: {
     command: electron,
     args: main

src/index.js

@@ -1,6 +1,6 @@
 var spawn = require('child_process').spawn;
 var chokidar = require('chokidar');
-var debug = require('debug');
+var debug = require('debug')('spawn-auto-restart');
 
 
 module.exports = function (options) {
@@ -11,9 +11,6 @@ module.exports = function (options) {
   var proc;
   var restarting = false;
 
-  if (options.debug) { debug.enable('spawn-auto-restart'); }
-  var log = debug('spawn-auto-restart');
-
   // allows use all options available for spawn
   var procCommand = options.proc;
   var procArgs;
@@ -53,7 +50,7 @@ module.exports = function (options) {
     };
 
     proc.on('error', function () {
-      log('restarting due error');
+      debug('restarting due error');
       restarting = true;
       proc.kill('SIGINT');
     });
@@ -66,7 +63,7 @@ module.exports = function (options) {
 
   // starts watching
   chokidar.watch(watchPath, watchOptions).on('change', function() {
-    log('restarting due changes');
+    debug('restarting due changes');
     restarting = true;
     proc.kill('SIGINT');
   });