Merge pull request #132 from treeowl/travis-update

Update .travis.yml per hvr's advice

.travis.yml

@@ -7,12 +7,13 @@ env:
  # no package for earlier cabal versions in the PPA
  - GHCVER=7.4.2 CABALVER=1.16
  - GHCVER=7.6.3 CABALVER=1.16
- - GHCVER=7.8.2 CABALVER=1.18
- - GHCVER=head  CABALVER=1.20
+ - GHCVER=7.8.4 CABALVER=1.18
+ - GHCVER=7.10.1 CABALVER=1.22
+ - GHCVER=head CABALVER=head
 
 matrix:
   allow_failures:
-   - env: GHCVER=head  CABALVER=1.20
+   - env: GHCVER=head CABALVER=head
 
 # Note: the distinction between `before_install` and `install` is not
 #       important.