upgrade mail_view
attach sparkline images inline

doesnt work in mailview
Merge branch 'master' into sparkline-inline

Conflicts:
	lib/tricle/presenters/metric.rb
	tricle.gemspec
Merge branch 'sparkline' into sparkline-inline

Conflicts:
	lib/tricle/aggregation.rb
	tricle.gemspec
Merge branch 'sparkline' into sparkline-inline
Merge pull request #60 from afeld/sparkline-inline

attach sparkline images inline