Issue 98 (#101)

* Add custom_css parameter.

* Copy documentation from hugo-octopress.

README.md

 _n.b. in future versions we will likely separate the typeface and other body classes._
 
 
+### Custom CSS
+
+You can override the built-in css by using your own. Just put your own css files in the `static` directory of your website (the one in the theme directory also works but is not recommended) and modify the `custom_css` parameter in your config file. The path referenced in the parameter should be relative to the `static` folder. These css files will be added through the `header` partial after the built-in css file.
+
+For example, if your css files are `static/css/custom.css` and `static/css/custom2.css` then add the following to the config file:
+
+```
+    [params]
+      custom_css = ["css/custom.css","css/custom2.css"]
+```
+
 ### Nearly finished
 
 In order to see your site in action, run Hugo's built-in local server.

layouts/_default/baseof.html

       <link href="{{ absURL (printf "%s%s" "/dist/" .) }}" rel="stylesheet">
     {{ end }}
 
+    {{ range .Site.Params.custom_css }}
+      <link rel="stylesheet" href="{{ $.Site.BaseURL }}{{ . }}">
+    {{ end }}
 
     {{ block "favicon" . }}
       {{ partial "site-favicon.html" . }}