Add mission and values admonitions (#322)

Author: jarrodmillman

layouts/shortcodes/admonition.html

@@ -26,6 +26,10 @@
 This is an important admonition.
 {{< /admonition >}}
 
+{{< admonition mission >}}
+This is our mission.
+{{< /admonition >}}
+
 {{< admonition note >}}
 This is a note admonition.
 {{< /admonition >}}
@@ -42,6 +46,10 @@
 This is a warning admonition.
 {{< /admonition >}}
 
+{{< admonition values >}}
+This is our values.
+{{< /admonition >}}
+
 */}}
 
 <div class="admonition {{ .Get 0 }}">