Prefer stow over hand-rolled solution

After discovering GNU stow on Nix IRC, refactored install and setup
scripts to consume it.

Code is vastly simplified as a result.

configs/shared/haskell/.ghci

@@ -0,0 +1,32 @@
+-- Useful Typeclasses
+import Control.Applicative
+import Data.Monoid
+
+-- Data Structures
+import qualified Data.Map.Internal as Map
+
+-- Lenses
+import           Control.Lens
+import qualified Control.Lens           as Lens 
+import qualified Control.Lens.Traversal as Lens
+
+-- Friendly prompt
+:set prompt "\ESC[34mλ> \ESC[m"
+
+-- GHCi on Acid
+:m - Prelude
+:m + GOA
+setLambdabotHome "/Users/wpcarro/Haskell/bin"
+:def bs        lambdabot "botsnack"
+:def pl        lambdabot "pl"
+:def unpl      lambdabot "unpl"
+:def redo      lambdabot "redo"
+:def undo      lambdabot "undo"
+:def index     lambdabot "index"
+:def docs      lambdabot "docs"
+:def instances lambdabot "instances"
+:def hoogle    lambdabot "hoogle"
+:def source    lambdabot "fptools"
+:def where     lambdabot "where"
+:def version   lambdabot "version"
+:def src       lambdabot "src"