Cabal options get overwritten by commandline options #52

hdevtools takes both GHC options from the cabal file of a project and on the commandline and appens the commandline options BEHIND the cabal options. However, this leads to annoying behaviour when using hdevtools together with, e.g. vim-hdevtools or syntastic which use a global "hdevtools_config" variable.

The problem is this:
If, in my vim config, I have the options -Wall -Wno-unused-do-binds (the default flags I want to use for checking haskell files in the absence of a cabal config) these get appended AFTER the options hdevtools has parsed from my cabal file. Suppose my cabal file has -Wall -Wno-unused-do-binds -Wno-orphans, then appending the -Wall -Wno-unused-do-binds from my vim config ends up overwriting the more project specific -Wno-orphans in my cabal file.

Solutions:

1. Append cabal options AFTER the commandline GHC options, letting the more specific options dominate. Pros: Trivial change. Cons: Maybe someone DOES want to override the cabal options on the commandline

2. Add a new way of specifying "default" GHC options, which are only used if no options are succesfully gotten from cabal.