Use a varying mochilo version in CI

.travis.yml

@@ -2,6 +2,9 @@ language: ruby
 rvm:
   - 2.3.3
   - 2.4.0
+gemfiles:
+  - gemfiles/mochilo-v1
+  - gemfiles/mochilo-v2
 env:
   - BERT_TEST_IMPL=Ruby
   - BERT_TEST_IMPL=C

gemfiles/mochilo-v1

@@ -0,0 +1,7 @@
+# frozen_string_literal: true
+# A sample Gemfile
+source "https://rubygems.org"
+
+gemspec
+
+gem "mochilo", :git => "https://github.com/spraints/mochilo", :ref => "v1-time-regexp"

gemfiles/mochilo-v2

@@ -0,0 +1,7 @@
+# frozen_string_literal: true
+# A sample Gemfile
+source "https://rubygems.org"
+
+gemspec
+
+gem "mochilo", :git => "https://github.com/spraints/mochilo", :ref => "symbols-and-regexps-and-time-oh-my"