Fix error in .travis.yml.

Author: ondrap

.travis.yml

@@ -1,7 +1,7 @@
 language: c
 sudo: false
 matrix:
- include:
+  include:
     - env: CABALVER=1.18 GHCVER=7.8.4
       addons: {apt: {packages: [cabal-install-1.18,ghc-7.8.4], sources: [hvr-ghc]}}
     - env: CABALVER=1.22 GHCVER=7.10.1