%section
  %h3=t("contributors.title")

  .row
    .col-md-12
      #map{ :style => "width: 100%; height: 300px;" }
      %p.text-muted=t("contributors.location_privacy")
      #maps-data.hidden
        = raw @map_markers.to_json
      %hr
  .row
    - users.each_slice(6) do |row|
      %ul.thumbnails.clearfix
        - row.each do |user|
          %li.collaborator.col-md-2
            .thumbnail
              = link_to image_tag(user.avatar_url(200), :width => 200, :height => 200, :alt => user.nickname).html_safe, user
              .caption
                %strong= link_to "@#{user.nickname}", user

  = javascript_include_tag "//maps.google.com/maps/api/js?v=3.18&sensor=false&client=&key=&libraries=geometry&language=&hl=&region="
  = javascript_include_tag "//google-maps-utility-library-v3.googlecode.com/svn/tags/markerclustererplus/2.0.14/src/markerclusterer_packed.js"
  = javascript_include_tag "maps"

%section
  %h3=t("contributors.title")

  .row
    .col-md-12
      #map{ :style => "width: 100%; height: 300px;" }
      %p.text-muted=t("contributors.location_privacy")
      #maps-data.hidden
        = raw @map_markers.to_json
      %hr
  .row
    - users.each_slice(6) do |row|
      %ul.thumbnails.clearfix
        - row.each do |user|
          %li.collaborator.col-md-2
            .thumbnail
              = link_to image_tag(user.avatar_url(200), :width => 200, :height => 200, :alt => user.nickname).html_safe, user
              .caption
                %strong= link_to "@#{user.nickname}", user

  = javascript_include_tag "//maps.google.com/maps/api/js?v=3.18&sensor=false&client=&key=&libraries=geometry&language=&hl=&region="
  = javascript_include_tag "//google-maps-utility-library-v3.googlecode.com/svn/tags/markerclustererplus/2.0.14/src/markerclusterer_packed.js"
  = javascript_include_tag asset_path('maps')

Use asset_path when loading maps.js
Use asset_path when loading maps.js