Update branch alias and travis

.travis.yml

@@ -8,7 +8,7 @@ services:
 
 env:
   global:
-    - COMPOSER_ROOT_VERSION=4.5.x-dev
+    - COMPOSER_ROOT_VERSION=4.6.x-dev
 
 matrix:
   include:
@@ -27,7 +27,7 @@ before_script:
 
   - composer validate
   - composer require --no-update silverstripe-themes/simple:~3.2.0
-  - if [[ $DB == PGSQL ]]; then composer require silverstripe/postgresql:2.1.x-dev --no-update; fi
+  - if [[ $DB == PGSQL ]]; then composer require silverstripe/postgresql:2.4.x-dev --no-update; fi
   - composer install --prefer-source --no-interaction --no-progress --no-suggest --optimize-autoloader --verbose --profile
 
   # Validate cow schema

composer.json

@@ -22,6 +22,9 @@
         "phpunit/phpunit": "^5.7"
     },
     "extra": {
+        "branch-alias": {
+            "4.x-dev": "4.6.x-dev"
+        },
         "project-files": [
             "app/src/*"
         ],