make it buildable on ghc 7.7.20131217

to have this package built on ghc 7.7.20131217 you explicitly need -dynamic-too option.
typo
Merge pull request #4 from ggreif/patch-1

typo
Fix issue #2.

Document that optimizing the result of singDecideInstance can cause
GHC 7.6.3 and lower to hang.
Merge pull request #3 from nushio3/patch-1

make it buildable on ghc 7.7.20131217