Merge branch 'feature/list-where' of git://github.com/zeckalpha/wren into zeckalpha-feature/list-where

Conflicts:
	builtin/core.wren
	src/wren_core.c

builtin/core.wren

@@ -16,7 +16,7 @@ class List {
     }
     return result
   }
-  
+
   map (f) {
     var result = []
     for (element in this) {
@@ -24,4 +24,12 @@ class List {
     }
     return result
   }
+
+  where (f) {
+    var result = []
+    for (element in this) {
+      if (f.call(element)) result.add(element)
+    }
+    return result
+  }
 }