#325

- 1), 2) should be fixed with this update
- 3) should be defined what should happen

Open question:

- I don't know if large and small should be exclusive or.
I guess so, but it was not.

Note:

- I tried to minimize updates to the btnClasses map but that didn't work
I filed a but, see code comment on method `updateBtnClassesJob()`

#786

- I think the button tests is thoroughly.
It can be refined of course if issues occur
or if someone has ideas what can be additionally tested

Note:

- drone.io doesn't install content_shell by default
this has to be done manually (I haven't done it myself yet)
if you add `test/run.sh` to the build script for drone.io the test will probably fail
Merge remote-tracking branch 'upstream/master' into merge-spark-button-changes

Conflicts:
	widgets/lib/spark_button/spark_button.dart
	widgets/lib/spark_button/spark_button.html
	widgets/pubspec.yaml
Upgrade spark-button test to new Polymer and new spark-button
Renamed test sources to disambiguate
Fix spark-button test (noPadding still fails due to a bug in spark-button itself)
Remove unnecessary delays from spark-button test
spark-button test: comments + additional CSS class check
Import, upgrade and fix the WIP spark-button test from @zoechi's pending PR #1430
Emulate a more realistic usage of spark-button in hypothetical code
Merge remote-tracking branch 'upstream/master' into upgrade-spark-button-test
Merge pull request #1878 from ussuri/upgrade-spark-button-test

Upgrade spark-button test