Adds option to disable CMake package exporting.
Set Pangolin_DIR for examples.

- Otherwise, it might not use the correct Pangolin or it won't find it
  if we don't export the package.
Added support for 'size' parameter for v4l video.
Merge pull request #2 from dgossow/master

Added support for 'size' parameter for v4l video.
Merge branch 'master' of github.com:gwu-robotics/Pangolin