Add matrix to Travis

Adding `matrix` to travis testing will allow Travis to parallel test
different builds in separate processes.
Use matrix for browser/build testing
Removing IE6 because it hangs up on Travis/Sauce
Removing sniffing in the test
fix unknown bug
Using outer element for testing
Merge pull request #2576 from SergioCrisostomo/matrix

Add matrix to Travis. Run parallel builds.
Merge pull request #2580 from kentaromiura/fix-unknown-error

fix unknown bug
Merge pull request #2579 from kentaromiura/fix-breaking-test

Removing sniffing in the test