Add unsafe version of init

Author: garyb

README.md

@@ -110,6 +110,8 @@
 
     head :: forall a. [a] -> a
 
+    init :: forall a. [a] -> [a]
+
     last :: forall a. [a] -> a
 
     tail :: forall a. [a] -> [a]

src/Data/Array/Unsafe.purs

@@ -1,7 +1,8 @@
 module Data.Array.Unsafe where
 
 import Prelude.Unsafe
-import Data.Array (length)
+import Data.Maybe.Unsafe
+import qualified Data.Array as A
 
 head :: forall a. [a] -> a
 head (x : _) = x
@@ -10,4 +11,7 @@ tail :: forall a. [a] -> [a]
 tail (_ : xs) = xs
 
 last :: forall a. [a] -> a
-last xs = unsafeIndex xs (length xs - 1)
+last xs = unsafeIndex xs (A.length xs - 1)
+
+init :: forall a. [a] -> [a]
+init = fromJust <<< A.init