Slack notifications for travis builds

And ignoring anvil build artifacts

.gitignore

@@ -4,3 +4,4 @@ dist
 cabal.sandbox.config
 hscope.out
 codex.tags
+.anvil

.travis.yml

@@ -2,6 +2,8 @@ language: haskell
 ghc: 7.8
 addons:
   postgresql: "9.3"
+notifications:
+  slack: looprecur:z2nPS2Cfx2D33LE2obyU2FyQ
 before_install:
   - createuser --superuser --no-password dbapi_test
   - createdb -O dbapi_test -U postgres dbapi_test