Bump to 1.5.0rc1 (#4318)

lib/mastodon/version.rb

@@ -9,23 +9,27 @@ module Mastodon
     end
 
     def minor
-      4
+      5
     end
 
     def patch
-      7
+      0
     end
 
     def pre
       nil
     end
 
+    def flags
+      'rc1'
+    end
+
     def to_a
       [major, minor, patch, pre].compact
     end
 
     def to_s
-      to_a.join('.')
+      [to_a.join('.'), flags].join
     end
   end
 end