Add a module to load JSON configuration files
Use a custom error when loading configurations
Add rule filtering to pa11y and the command-line tool
Write feature tests for config files/ignoring rules
Reduce the output of the console reporter, and include codes
Document the new config option
Require config JSON file using CWD
Use path.resolve to resolve config file path
use the local `.pa11yrc` when no config is provided

this should close #21
Stop using require for config loading – we only want JSON
Write more extensive feature tests for the config option
Fix typo