docs: Replaced Slack with official Gitter channel

_config.yml

@@ -34,7 +34,7 @@ social_image_path: /assets/brand/bootstrap-social.png
 current_version:  4.0.0-beta.3
 docs_version:     4.0
 repo:             https://github.com/FezVrasta/bootstrap-material-design
-slack:            https://bootstrap-slack.herokuapp.com
+gitter:           https://gitter.im/FezVrasta/bootstrap-material-design
 
 download:
   source:         https://github.com/FezVrasta/bootstrap-material-design/releases

_includes/docs-navbar.html

@@ -49,8 +49,8 @@
       </a>
     </li>
     <li class="nav-item">
-      <a class="nav-link p-2" href="{{ site.slack }}" target="_blank" rel="noopener" aria-label="Slack">
-        {% include icons/slack.svg class="navbar-nav-svg" %}
+      <a class="nav-link p-2" href="{{ site.gitter }}" target="_blank" rel="noopener" aria-label="Gitter">
+        {% include icons/gitter.svg class="navbar-nav-svg" %}
       </a>
     </li>
   </ul>

_includes/icons/gitter.svg

@@ -0,0 +1,6 @@
+<svg{% if include.class %} class="{{ include.class }}"{% endif %} xmlns="http://www.w3.org/2000/svg" viewbox="0 0 512 512"{% if include.width %} width="{{ include.width }}"{% endif %}{% if include.height %} height="{{ include.height }}"{% endif %} focusable="false"><title>Gitter</title>
+<rect x="115.9" y="26.2" width="40" height="297.6" fill="currentColor"/>
+<rect x="358.9" y="94.5" width="40" height="229.3" fill="currentColor"/>
+<rect x="196.4" y="94.5" width="40" height="391.3" fill="currentColor"/>
+<rect x="277.9" y="94.5" width="40" height="391.3" fill="currentColor"/>
+</svg>

assets/css/docs.css

@@ -142,7 +142,7 @@
   display: block;
   color: #777 !important; }
 
-.partner {
+.partner.mdbootstrap {
   display: none; }
 
 .bd-content {