Update travis to support Qt 5.6
Update travis to support Qt 5.6

The qt55 repository disappeared.

Signed-off-by: Thiago Macieira <0ed1648d92ca0373297a182b1dba1b974ad10d88@intel.com>

01org/tinycbor,01org/tinycbor,intel/tinycbor,thiagomacieira/tinycbor,thiagomacieira/tinycbor,thiagomacieira/tinycbor,01org/tinycbor,thiagomacieira/tinycbor,intel/tinycbor,intel/tinycbor,intel/tinycbor