.travis.yml: add slack notifications -> #build-notices
.travis.yml: add slack notifications -> #build-notices

Change-Id: I975a9b73c3ba3cac291d71e12cd584bbe077e562
Signed-off-by: Manoel Vilela <1842af20ff2af0abd9d9cfd36b150514d5495d28@engineer.com>

GanShun/u-root,u-root/u-root,rminnich/u-root,u-root/u-root,rminnich/u-root,rminnich/u-root,hugelgupf/u-root,hugelgupf/u-root,GanShun/u-root,u-root/u-root,hugelgupf/u-root,hugelgupf/u-root,rminnich/u-root,GanShun/u-root