gazebo8 8.3.0 (#376)
gazebo8 8.3.0 (#376)

* gazebo8 8.3.0

* remove tinyxml patch

* gazebo8 8.3.0 sierra bottle

* gazebo8 8.3.0 el_capitan bottle

* gazebo8 8.3.0 high_sierra bottle

scpeters/homebrew-simulation,osrf/homebrew-simulation,j-rivero/homebrew-simulation