Travis-ci: Only test Rails master with Ruby 2.2

and without Mongo DB for now.

.travis.yml

@@ -11,11 +11,6 @@ rvm:
   - 1.9
 
 env:
-  - RAILS=master DB=mongodb
-  - RAILS=master DB=sqlite3
-  - RAILS=master DB=mysql
-  - RAILS=master DB=postgres
-
   - RAILS=4-2-stable DB=mongodb
   - RAILS=4-2-stable DB=sqlite3
   - RAILS=4-2-stable DB=mysql
@@ -43,20 +38,30 @@ env:
   - RAILS=3-0-stable DB=postgres
 
 matrix:
-  exclude:
-    - rvm: 1.9
-      env: RAILS=master
-    - rvm: 2.0
-      env: RAILS=master
+  include:
+    - rvm: 2.2
+      env: RAILS=master DB=sqlite3
+    - rvm: 2.2
+      env: RAILS=master DB=mysql
+    - rvm: 2.2
+      env: RAILS=master DB=postgres
+
   allow_failures:
-    - env: RAILS=master DB=mongodb
     - env: RAILS=master DB=sqlite3
     - env: RAILS=master DB=mysql
     - env: RAILS=master DB=postgres
     - rvm: 2.2
-      env: RAILS=3-2-stable
-      env: RAILS=3-1-stable
-      env: RAILS=3-0-stable
+      env: RAILS=3-2-stable DB=sqlite
+      env: RAILS=3-2-stable DB=mysql
+      env: RAILS=3-2-stable DB=postgres
+    - rvm: 2.2
+      env: RAILS=3-1-stable DB=sqlite
+      env: RAILS=3-1-stable DB=mysql
+      env: RAILS=3-1-stable DB=postgres
+    - rvm: 2.2
+      env: RAILS=3-0-stable DB=sqlite
+      env: RAILS=3-0-stable DB=mysql
+      env: RAILS=3-0-stable DB=postgres
 
 before_script:
   - mysql -e 'create database ransack collate utf8_general_ci;'