Temporary restrict Roda version in CI on Ruby <2.3

One of the Rails 4 monkey patches breaks Roda's capture_erb
plugin after the changes in Roda 3.82.  I think I'll fix
this in Roda, but in the meantime, this should get CI passing.

.ci.gemfile

@@ -1,11 +1,16 @@
 source 'https://rubygems.org'
 
 gem "minitest-global_expectations"
-gem "roda"
 gem "rack_csrf"
 gem "erubi", '>= 1.13'
 gem "tilt"
 
+if RUBY_VERSION < '2.3'
+  gem "roda", '< 3.82'
+else
+  gem "roda"
+end
+
 if RUBY_VERSION < '2.0'
   gem 'mime-types', '< 2'
   gem 'concurrent-ruby', '<1.1.10'