A fullish suite of tests.

[sanason]

This PR adds automated tests to replace the suite of tests that are run manually for each DAP code release (the manual testing has traditionally been performed by our Google Analytics partner). A spreadsheet documenting the the old manual test suite is here (only accessible to internal TTS people). I've added a column showing which automated test each of the old manual tests map to.

Several things that are missing from the automated tests as compared to the manual tests:

1. I didn't completely finish covering everything in the spreadsheet.
2. The spreadsheet is for DAP v8.2, which is almost 2 years old. Features have been added since then and need to be tested too. The spreadsheet came from our GA partners - we need to get a new copy from them.
3. The spreadsheet suggests that manual testing is performed against Chrome, Firefox and Safari. The automated tests only test against Chrome.
4. The manual tests involve three layers of testing (see below). The automated tests are primarily "code level" tests. See the testing README for a discussion of whether that level of testing is sufficient.
   • Code Level: Validating correct syntax insertion.
   • Hit Level: Monitoring the GIF requests that are sent to the Google Analytics servers by using a tool like Firebug on Firefox or the Google Analytics Debugger extension for Google Chrome.
   • Data Collection Level: Validating data in GA reports after data processing.