Bump rexml from 3.2.8 to 3.3.6 (#45)

Gemfile.lock

@@ -126,8 +126,8 @@ GEM
     public_suffix (4.0.7)
     rake (13.0.6)
     rchardet (1.8.0)
-    rexml (3.2.8)
-      strscan (>= 3.0.9)
+    rexml (3.3.6)
+      strscan
     ruby-macho (2.5.1)
     ruby2_keywords (0.0.5)
     sawyer (0.9.2)
@@ -142,13 +142,13 @@ GEM
     tzinfo (2.0.6)
       concurrent-ruby (~> 1.0)
     unicode-display_width (2.5.0)
-    xcodeproj (1.23.0)
+    xcodeproj (1.25.1)
       CFPropertyList (>= 2.3.3, < 4.0)
       atomos (~> 0.1.3)
       claide (>= 1.0.2, < 2.0)
       colored2 (~> 3.1)
       nanaimo (~> 0.3.0)
-      rexml (~> 3.2.4)
+      rexml (>= 3.3.6, < 4.0)
 
 PLATFORMS
   ruby