Liquid tag and HTML entity support

Merge pull request #10 from jrha/liquid

Strip and ignore fancier markdown link types and liquid tags

1.3: Merge pull request #7 from jrha/master

Bugfixes

1.2: Merge pull request #6 from jrha/cli

Only report lines with errors and fix unit tests

1.1: Merge pull request #5 from jrha/cli

Fix interpretation of boolean check state option

1.0: Merge pull request #4 from jrha/cli

Improve CLI experience