Using cross-spawn as a drop-in for child_process

Until nodejs/node-v0.x-archive#2318 is resolved, opting for `cross-spawn` instead of
using `child_process` directly to provide better windows compatibility.

Resolves #30

Author: ethul

package.json

@@ -29,6 +29,7 @@
     "purescript"
   ],
   "dependencies": {
+    "cross-spawn": "^0.4.0",
     "glob": "^5.0.5",
     "gulp-util": "^3.0.4",
     "logalot": "^2.1.0",

src/ChildProcess.purs

@@ -17,7 +17,7 @@ spawn command args = makeAff $ runFn4 spawnFn command args
 foreign import spawnFn """
 function spawnFn(command, args, errback, callback) {
   return function(){
-    var child_process = require('child_process');
+    var child_process = require('cross-spawn');
 
     var process = child_process.spawn(command, args);