Added MonadError's instance for Compiler.
Added MonadError's instance for Compiler.

oldmanmike/hakyll,Javran/hakyll,beni55/hakyll,freizl/freizl.github.com-old,freizl/freizl.github.com-old,freizl/freizl.github.com-old,d12frosted/hakyll,freizl/freizl.github.com-old,freizl/freizl.github.com-old,Minoru/hakyll,freizl/freizl.github.com-old,freizl/freizl.github.com-old