Bump rexml from 3.2.6 to 3.2.8 (#44)

Author: dependabot[bot]

Gemfile.lock

@@ -126,12 +126,14 @@ GEM
     public_suffix (4.0.7)
     rake (13.0.6)
     rchardet (1.8.0)
-    rexml (3.2.6)
+    rexml (3.2.8)
+      strscan (>= 3.0.9)
     ruby-macho (2.5.1)
     ruby2_keywords (0.0.5)
     sawyer (0.9.2)
       addressable (>= 2.3.5)
       faraday (>= 0.17.3, < 3)
+    strscan (3.1.0)
     terminal-table (3.0.2)
       unicode-display_width (>= 1.1.1, < 3)
     thor (0.20.3)