Adding a global default timeout for all wait functions.

[mengchen2]

This PR is Addressing Issue #81.
Adding nemo.view.defaultTimeout as a new name space for Nemo-view.

Usage:
Add global waitTimeout on config.json:

  "plugins": {
    "view": {
      "module": "nemo-view",
      "arguments": [ "path:../../node_modules/gctnightswatchnodeweb/locator", 30000]
    },

If no timeout value provided to the plugin arguments, Nemo-view will use the fallback timeout, which is 5000. Just like before

  "plugins": {
    "view": {
      "module": "nemo-view",
      "arguments": [ "path:../../node_modules/gctnightswatchnodeweb/locator"]
    },

Another way to use it, set timeout for the case:
nemo.view.defaultTimeout = 60000;

[grawk]

1. Please don't add another property to nemo.view (see more detailed comment)
2. would need to add this new argument to the README
3. please add a CHANGELOG entry

[grawk]

Instead of this, please pass the defaultTimeout as a parameter to the view class. Adding it to the nemo.view namespace may potentially collide with a user defined view.

[grawk]

Thanks @mengchen2 .. I had started working on this over the weekend but it's only a local working copy. It differs from yours in terms of passing the timeout value as a parameter to the "locreator" class. I would recommend that approach.