adding doc.
user package db options for both GHC and ghc-pkg.
M-C-d now can display the doc even in the sandbox.
the format of hlint options.
removing comment.
error handling for hlint.
hlint hack.
hlint options.
hlint options.
fixing a bug of hlint options.
fixing a bug of ghc-debug.
C-cC-k kills a process.
handling multiple package names from ghc-pkg find-module.
removing dep packages of benchmark.

installing packages of benchmark fails in many cases, sigh.
supporting sandbox only (without cabal) to fix #164.