Fix active callback multi load

[dengjeffrey]

What this PR tries to accomplish

• Fixes active-event not being triggered when two calls made back to back #309
  • Fire the active event, even if WebFont.load is called multiple times in succession

How it accomplishes them

Fixes #309

• Adds an object FontModulesLoadCounter to keep track of the modules being loaded and which is the last one being processed as part of a WebFont.load request
• Breaks down the methods in FontWatchRunner and NativeFontWatchRunner so that they are easier to test using jasmine
• Adds an additional test to the webfont.spec to test that the active event triggers twice for two WebFont.load calls

[nuthinking]

Interesting improvement. Shame the repo is abandoned.