Modify ParsingServiceProvider

Modify HaikMarkdown constructor
Add haik.markdown config
Rename dir name
Modify page seeder.

Modify body of SiteNav page
Add markdown parser for nav

NavParser is incomplete
Add NavPlugin for parser
Merge branch 'master' into feature-nav-plugin
Merge branch 'master' into feature-nav-plugin
Modify seeder
Modify NavParser reduce special attributes features
Modify NavParser
Modify NavPlugin

Add tests
Add modules of NavPlugin.

* Special Button plugin
* Special PluginRepository
Merge remote-tracking branch 'origin/master' into feature-nav-plugin
Merge pull request #20 from hokuken-inc/feature-nav-plugin

Feature nav plugin