support I18N (not finished) (thanks takahashim)

Import from  https://github.com/takahashim/mrubysearch/commit/cfaacc6430f39821338fc81a99a523e757d5affa
locale can be changed with URL params like "?locale=en" and stored in sessions (cookies) (thanks takahashim)

Import from  https://github.com/takahashim/mrubysearch/commit/798de545e880c4ce97d96be1f2ec9703cdf780e1
'Recently Viewd' -> 'Recently'
Add <br>
Tweak text
Remove  unexpected merge
Add 'i18n' to Gemfile
Support to reload with sinatra-reloader
Pass test_cdweb_app.rb

'session' variable can't find during testing
Add translation
Add translation
Merge branch 'feature/i18n' into develop
Had forgotten Regexp.escape
Add DocumentTable#drilldown(result, column, num)
Add SearchContents#drilldown_contents
Change Groonga::Schema table.text(“suffix”) -> table.string(“suffix”)

Need ‘milk rebuild --all’
Implement filter of suffix
Add .filter_list class and Adjust css
Tweak 5 -> 8
Add translation :filter_by_package and :filter_by_suffix