add GPIO 4 emergency pause

cli

@@ -19,8 +19,7 @@ function start() {
 
     pm2.start({
       script: path.join(__dirname,'index.js'),
-      name: 'xcarve',
-      cwd: process.cwd()
+      name: 'xcarve'
     }, (err, apps) => {
       pm2.disconnect();
       if (err) throw err

lib/websocket_controller.js

@@ -1,12 +1,16 @@
 // this file is part of the v0.2.7 easel local OS X install.
 // you can find out more about easel and the x-carve at
 // inventables.com & easel.inventables.com
-
 var Machine = require('./machine')
   , SerialPortController = require('./serial_port_controller')
   , path     = require('path')
   , Debugger = require('./debugger')
-  , power = require('onoff').Gpio(17, 'out') , fs = require('fs'); var WebsocketController = function(sockets, version, abilities) { var that = {};
+  , power = require('onoff').Gpio(17, 'out')
+  , estop = require('onoff').Gpio(4, 'in', 'both')
+  , fs = require('fs');
+
+var WebsocketController = function(sockets, version, abilities) {
+  var that = {};
   var logger = Debugger.logger("Websocket Controller");
   var connectedClients = 0;
   var serialPortController = new SerialPortController();
@@ -232,6 +236,11 @@ var Machine = require('./machine')
     echoEnabled = enabled;
   };
 
+  estop.watch(function (err, value) {
+    if(err || !value)
+      machine.pause();
+  });
+
   sockets.on('connection', function(socket) {
 
     // turn on powerswitchtail