Add compatibility with Webpack as a RequireJS alternative

In an effort to move our apps from RequireJS to Webpack, I ran into only one package that wouldn't work straight out of the box -- this one. FlightJS was hassle-free, as was jasmine-jquery, so I prepared this PR which is a working implementation of supporting both Webpack and RequireJS.

Unfortunately the API for `describeComponent`, `describeMixin` and `describeModule` had to become more liberal in the process, eg:

```javascript
// RequireJS usage:
describeComponent('ui/activity-list', ...
```
vs
```javascript
// Webpack usage:
describeComponent(require('ui/activity-list'), ...
```

The other change is that the encapsulation of the plugin failed to have a working reference to `jasmine`. After a few false-starts and some horrible hacks I instead replicated the format used by jasmine-jquery, which was already compatible with both bundling tools.

The patch passes jasmine-flight's tests as well as 99designs' largest two jasmine-flight suites under both Webpack and RequireJS; hopefully this is something you'll consider merging. Thanks.