Install the newest version of dub to avoid random network failures

.travis.yml

@@ -38,6 +38,13 @@ matrix:
     - d: dmd
       env: CONFIG='select' DUB_FLAGS='--build unittest-cov --build-mode=singleFile'
 
+
+before_install:
+  # Use the dub-updating fork of the installer script until https://github.com/dlang/installer/pull/301 is merged
+  - wget https://raw.githubusercontent.com/wilzbach/installer-dub/master/script/install.sh -O ~/dlang/install.dub.sh
+  - . $(bash ~/dlang/install.dub.sh -a dub)
+  - dub --version
+
 script: ./travis-ci.sh
 
 sudo: false