Add sample humanstxt plugin.

That plugin shows an simple example how add additional
urlmappings and additional templates to the project.
Add ngRoute dependency to taigaPlugins module.
Add gulp task for copy plugins templates.
Add express/gulp url for serve plugins directory in development server.
Rename humanstxt to humanshtml
Merge pull request #10 from taigaio/saas-layer-examples

Saas layer examples.