Implement basic navbar

Signed-off-by: Tobias Eidelpes <tobias@eidelpes.info>

app/helpers/application_helper.rb

@@ -1,2 +1,22 @@
 module ApplicationHelper
+  # Contains the complete navbar
+  def nav_bar
+    content_tag(:div, class: 'topnav', id: 'topnav') do
+      yield
+    end
+  end
+
+  # Defines individual links in the navbar. To be used inside nav_bar
+  def nav_link(text, path)
+    # Sets active class on the link corresponding to the page being viewed
+    options = current_page?(path) ? { class: 'active' } : {}
+    link_to text, path, options
+  end
+
+  # Used to render svg image files
+  def show_svg(path)
+    File.open("app/assets/images/#{path}", 'rb') do |file|
+      raw file.read
+    end
+  end
 end