Update subdue for 0.26

[jaxxstorm]

In 0.26, the subdue logic changed. It now only operates client side, and the hash config changed slightly.

• Remove subdue from the handler side configuration
• Add test coverage which covers the new handler specification on the check side
• Make sure subdue can be removed from the config see subdue should be optional for sensu check definition #548 and sensu::check unable to remove a check property #535

[ttarczynski]

@jaxxstorm I've tried to address the first two points in #563 and #564

[ttarczynski]

I've also tried to address the third point in #565
It allows to remove subdue with:

subdue => `absent'

[jaxxstorm]

@ttarczynski thanks for all the hard work!