Add PointXYZRGBNormal to PCL_ONLY_CORE_POINT_TYPES

Needed since 96f1c162e7f6dfb2aa6da7c2bd0b4fd22ae615f4
Don't run the Brisk unit test when there is no SSE4.1 available
Simplify Travis build script

- Compile using minimal build flags because of segfaults when using
  processor optimized builds.
Merge pull request #153 from jspricke/travis-cmake-test

Fix Travis build