Test with latest DMD versions.

.travis.yml

@@ -5,11 +5,12 @@ d:
   # this way the overall test time gets cut down (GDC/LDC are a lot
   # slower tham DMD, so they should be started early), while still
   # catching most DMD version related build failures early
-  - dmd-2.072.1
+  - dmd-2.072.2
   - dmd-2.070.2
   - ldc-1.0.0
   - ldc-1.1.0-beta6
   - dmd-2.071.2
+  - dmd-beta
 
 env:
     - CONFIG=select
@@ -19,6 +20,7 @@ env:
 matrix:
   allow_failures:
     - env: CONFIG=libasync
+    - d: dmd-beta
 
 script: ./travis-ci.sh