Fix console-patching for IE8/9
Fix console-patching for IE8/9

Hi,

using version 0.16.6. we're getting a 'console undefined' error in IE9.
I've traced it back to this attempt to monkey-patch the console.assert function, which is... well, not working at all ;)

```javascript
if (__global.console)
    console.assert = console.assert || function() {};
```

so I replaced it with this:

```javascript
  if (!__global.console) {
      __global.console = { assert: function() {} };
  }
```

Hope, that's all right.
vladima/es6-module-loader,vladima/es6-module-loader