Make last parameter a string

Author: danielpclark

lib/faster_path/optional/monkeypatches.rb

@@ -89,7 +89,7 @@ def relative?
         end
 
         def relative_path_from(other)
-          FasterPath.relative_path_from(@path, Pathname(other))
+          FasterPath.relative_path_from(@path, other)
         end
       end
     end

lib/faster_path/optional/refinements.rb

@@ -84,7 +84,7 @@ def relative?
       end
 
       def relative_path_from(other)
-        FasterPath.relative_path_from(@path, Pathname(other))
+        FasterPath.relative_path_from(@path, other)
       end
     end
   end

src/lib.rs

@@ -146,10 +146,11 @@ methods!(
 
   // fn r_split_names(pth: RString){}
 
-  fn pub_relative_path_from(itself: RString, base_directory: RString) -> Pathname {
-    pathname::pn_relative_path_from(itself, base_directory).map_err(|e| {
-      raise(e);
-    }).unwrap()
+  fn pub_relative_path_from(itself: RString, base_directory: AnyObject) -> Pathname {
+    let to_string = |i: AnyObject| { RString::from(i.send("to_s", None).value()) };
+
+    pathname::pn_relative_path_from(itself, base_directory.map(to_string)).
+      map_err(|e| raise(e) ).unwrap()
   }
 
   // fn pub_rmtree(pth: RString) -> NilClass {