BUG: Fix `qiime tools peek` for visualizations (#102)
BUG: Fix `qiime tools peek` for visualizations (#102)

Visualizations have a `format` of `None` which did not work with `click.secho`. The "Data format:" section of the output is now omitted for visualizations as it is not relevant.
qiime2/q2cli,jakereps/q2cli,jakereps/q2cli,gregcaporaso/q2cli,qiime2/q2cli,jairideout/q2cli,gregcaporaso/q2cli,jairideout/q2cli