Don’t show styleguide on live environment

Its audience is people working on the product, not the end users.

app/main/views/styleguide.py

@@ -1,4 +1,4 @@
-from flask import render_template
+from flask import render_template, current_app, abort
 from flask_wtf import Form
 from wtforms import StringField, PasswordField, TextAreaField, FileField, validators
 from app.main import main
@@ -7,6 +7,9 @@ from app.main import main
 @main.route('/_styleguide')
 def styleguide():
 
+    if not current_app.config['SHOW_STYLEGUIDE']:
+        abort(404)
+
     class FormExamples(Form):
         username = StringField(u'Username')
         password = PasswordField(u'Password', [validators.required()])