revert last travis changes

.travis.yml

@@ -1,8 +1,9 @@
 language: r
 r: bioc-devel
 cache: packages
-sudo: true       # use container based build system
+sudo: false       # use container based build system
 warnings_are_errors: true
+dist: trusty
 
 # Set CXX1X for R-devel, as R-devel does not detect CXX1X support for gcc 4.6.3,
 # this was causing mzR installation to fail
@@ -14,7 +15,6 @@ before_install:
 addons:
   apt:
     packages:
-      - libmagick++-dev
       - libnetcdf-dev
       - netcdf-bin # libnetcdf-dev doesn't contain nc-config in ubuntu 12.04 (in 16.04 it is part of libnetcdf-dev)
       - libhdf5-dev