ENH: Connect metadata summary button to handler

The "Show Metadata Summary" button now links to the metadata summary
handler.
Merge branch 'master' of git://github.com/biocore/qiita into gui-metadata-summary
BUG: Add prep_template_id to self.render blocks
Merge pull request #417 from ElDeveloper/gui-metadata-summary

ENH: Connect metadata summary button to handler