Follow up on skinning issues

- When running, the following error shows in the logs:

```
[2013-03-28T16:34:03.451Z] ERROR: oae/27219 on Nicolaass-MacBook-Pro.local: An uncaught exception was raised to the application.
    TypeError: Cannot read property 'BASE_SKIN' of undefined
        at EventEmitter.updateFileCaches (/Users/nicolaas/Desktop/SakaiOAE/ui/newOAE/Hilary/node_modules/oae-ui/lib/api.js:120:45)
        at EventEmitter.emit (events.js:98:17)
        at exports.createMonitor (/Users/nicolaas/Desktop/SakaiOAE/ui/newOAE/Hilary/node_modules/watch/main.js:117:13)
        at StatWatcher.exports.watchTree.fileWatcher (/Users/nicolaas/Desktop/SakaiOAE/ui/newOAE/Hilary/node_modules/watch/main.js:72:38)
        at StatWatcher.EventEmitter.emit (events.js:91:17)
        at StatWatcher._handle.onchange (fs.js:886:10)
```

- Building occasionally fails, presumably because the new skin file is not generated in time.

```
AssertionError: "123456" == "eceae5"
      at checkSkin (/home/travis/build/sakaiproject/Hilary/node_modules/oae-ui/tests/test-ui.js:262:24)
      at Request._callback (/home/travis/build/sakaiproject/Hilary/node_modules/oae-rest/lib/util.js:197:16)
      at Request.init.self.callback (/home/travis/build/sakaiproject/Hilary/node_modules/request/index.js:142:22)
      at Request.EventEmitter.emit (events.js:99:17)
      at Request.onResponse (/home/travis/build/sakaiproject/Hilary/node_modules/request/index.js:856:14)
      at Request.EventEmitter.emit (events.js:126:20)
      at IncomingMessage.Request.onResponse.buffer (/home/travis/build/sakaiproject/Hilary/node_modules/request/index.js:808:12)
      at IncomingMessage.EventEmitter.emit (events.js:126:20)
      at IncomingMessage._emitEnd (http.js:366:10)
      at HTTPParser.parserOnMessageComplete [as onMessageComplete] (http.js:149:23)
  2) UI Skinning verify that variables get updated with values from the config:
      
      actual expected
      
      1234eceae56
      
  AssertionError: "eceae5" == "123456"
      at checkSkin (/home/travis/build/sakaiproject/Hilary/node_modules/oae-ui/tests/test-ui.js:262:24)
      at Request._callback (/home/travis/build/sakaiproject/Hilary/node_modules/oae-rest/lib/util.js:197:16)
      at Request.init.self.callback (/home/travis/build/sakaiproject/Hilary/node_modules/request/index.js:142:22)
      at Request.EventEmitter.emit (events.js:99:17)
      at Request.onResponse (/home/travis/build/sakaiproject/Hilary/node_modules/request/index.js:856:14)
      at Request.EventEmitter.emit (events.js:126:20)
      at IncomingMessage.Request.onResponse.buffer (/home/travis/build/sakaiproject/Hilary/node_modules/request/index.js:808:12)
      at IncomingMessage.EventEmitter.emit (events.js:126:20)
      at IncomingMessage._emitEnd (http.js:366:10)
      at HTTPParser.parserOnMessageComplete [as onMessageComplete] (http.js:149:23)
```