Add fs.size() (#4)

fs.moon

@@ -1,10 +1,23 @@
 exists = (file_path) ->
-  handle = io.open file_path, "r"
-  if handle
-    handle\close!
+  if file = io.open file_path, "r"
+    file\close!
     return true
-  return false
+  else
+    return false
+
+size = (file_or_path) ->
+  if "string" == type file_or_path
+    file = io.open file_or_path, "r"
+    size = file\seek "end"
+    file\close!
+    return size
+  else
+    current = file\seek!
+    size = file\seek "end"
+    file\seek "set", current
+    return size
 
 {
   :exists
+  :size
 }