Add GHC-7.8.1-rc2.
Merge pull request #1921 from kosmikus/ghc-7.8.1

Add GHC-7.8.1-rc2.
haskell-hsini: update to version 0.3.1
haskell-network-conduit: update to version 1.0.4
haskell-persistent-postgresql: update to version 1.3.0.3
haskell-persistent-sqlite: update to version 1.3.0.3
haskell-persistent-template: update to version 1.3.1.2
haskell-persistent: update to version 1.3.0.3
haskell-pool-conduit: update to version 0.1.2.1
haskell-shelly: update to version 1.5.0.1
haskell-sqlite-simple: update to version 0.4.5.2
haskell-tasty-rerun: update to version 1.1.2
haskell-warp: update to version 2.1.1
haskell-yesod-bin: update to version 1.2.7.1
haskell-yesod-form: update to version 1.3.7
haskell-hlint: update to version 1.8.58