gnucash master: Fix travis config for master

[Geert Janssens]

Updated	 via  https://github.com/Gnucash/gnucash/commit/d4af95d6 (commit)
	from  https://github.com/Gnucash/gnucash/commit/fc41cd5c (commit)



commit d4af95d631ba45b2e1b2aeb53a1a37f8b461cc14
Author: Geert Janssens <janssens-geert at telenet.be>
Date:   Wed Nov 4 21:38:07 2015 +0100

    Fix travis config for master
    
    - use more recent base system, which brings in a more recent gcc version
    - install boost (currently 1.54)
    - skip explicit installation of packages that were installed already



Summary of changes:
 .travis.yml | 10 ++++++++--
 1 file changed, 8 insertions(+), 2 deletions(-)