test ApplicationHelper#tag_links_for
test ApplicationHelper#datestamp.
test and refactor EventsHelper#tweet_text.
test EventsHelper#today_tomorrow_or_weekday.
refactor MappingHelper.
remove untested and unused relative option in TimeRange.
test SourcesHelper.
the id is germane to the test.
force deterministic tag ordering.
test SiteController.
minor refactor.
test VersionsController.
Merge pull request #178 from botandrose/coverage

Increase test coverage
REBASE: Remove device width query to choose stylesheet; clone mobile CSS file as 'responsive.css' as a starting place for building a global, mobile-first, responsive design; bump font size up to 100%; begin the process of merging mobile and desktop styles
light refactoring of SourcesController.
extract duplication from SourcesController#create and #update.
initial extraction of Source::Importer.
minor refactor of Source::Importer.
simplify interface between SourcesController and Source::Importer.
move failure message over to Source::Importer.