Add travis config for ghc head without testsuite enabled

Currently the testsuite deps do not build with ghc head

Author: dcoutts

.travis.yml

@@ -31,6 +31,9 @@ matrix:
     - env: CABALVER=1.22 GHCVER=7.10.1
       compiler: ": #GHC 7.10.1"
       addons: {apt: {packages: [cabal-install-1.22,ghc-7.10.1,zlib1g-dev], sources: [hvr-ghc]}}
+    - env: CABALVER=head GHCVER=head NOTEST=1
+      compiler: ": #GHC head"
+      addons: {apt: {packages: [cabal-install-head,ghc-head,zlib1g-dev], sources: [hvr-ghc]}}
     - env: CABALVER=head GHCVER=head
       compiler: ": #GHC head"
       addons: {apt: {packages: [cabal-install-head,ghc-head,zlib1g-dev], sources: [hvr-ghc]}}