Replace raphael-rails with raphael.js and split it from the rest of the JS

What does this MR do?

Removes raphael.js and its related libraries from the default JS bundle.

It also removes raphael-rails because the gem is unmaintained and – for whatever reason – didn't want to cooperate with the way I was trying to require it.

This brings the default (compressed and minified) application.js from 354KB after the d3 MR (!4394 (merged)) down to 324KB.

Are there points in the code the reviewer needs to double check?

That tests pass and that there aren't errors on any pages (especially the Network page).

Why was this MR needed?

It's only used on the Network page and was using way too much bandwidth for just one page.

What are the relevant issue numbers?

#14372 (closed) #13165 (closed)

Follow-up to !4394 (merged) and !4516 (merged).

cc: @jschatz1

app/assets/javascripts/network/application.js.coffee

+# This is a manifest file that'll be compiled into including all the files listed below.
+# Add new JavaScript/Coffee code in separate files in this directory and they'll automatically
+# be included in the compiled file accessible from http://example.com/assets/application.js
+# It's not advisable to add code directly here, but if you do, it'll appear at the bottom of the
+# the compiled file.
+#
+#= require raphael
+#= require g.raphael
+#= require g.bar
+#= require_tree .
+
+$ ->
+  network_graph = new Network({
+    url: $(".network-graph").attr('data-url'),
+    commit_url: $(".network-graph").attr('data-commit-url'),
+    ref: $(".network-graph").attr('data-ref'),
+    commit_id: $(".network-graph").attr('data-commit-id')
+  })
+
+  new ShortcutsNetwork(network_graph.branch_graph)