Add some tests that use .options.json

[sidkshatriya]

As a by product of #96, a useful testing feature was built and that was the ability for a test to get arbitrary options from a .options.json file. See PR #98 for more details.

We can use this feature to add a couple of tests that will test some additional aspects of the amp-library:

• Add a test to check the addition of statistics html comment. Make sure that only the relevant statistics comments gets compared (e.g. number of tags processed) and not things like date (which would vary from run to run). For this make appropriate code changes.
• Add a test to see if <div placeholder> text is generated in the video to amp-video conversion.

[sidkshatriya]

All items complete on this ticket and the PR was merged to master. Closing.

[sidkshatriya]

I had an idea for some more tests. Re-opening this ticket.

[sidkshatriya]

There are 2 new tests.

• Test to test the no_lines = false feature (i.e. line number in "ampized" output)
• Test to test the diff feature

Closing.