Support Rails 4.2 even though I won't advertise it

I was thinking of making two releases, but I'll keep this one Rails 4.2
compatible. However, I won't support Ruby 1.9.3.

lib/web_console/extensions.rb

@@ -1,17 +1,20 @@
 ActionDispatch::DebugExceptions.class_eval do
   def render_exception_with_web_console(request, exception)
     render_exception_without_web_console(request, exception).tap do
-      backtrace_cleaner = request.env['action_dispatch.backtrace_cleaner']
+      # Retain superficial Rails 4.2 compatibility.
+      env = Hash === request ? request : request.env
+
+      backtrace_cleaner = env['action_dispatch.backtrace_cleaner']
       error = ActionDispatch::ExceptionWrapper.new(backtrace_cleaner, exception).exception
 
       # Get the original exception if ExceptionWrapper decides to follow it.
-      request.env['web_console.exception'] = error
+      env['web_console.exception'] = error
 
       # ActionView::Template::Error bypass ExceptionWrapper original
       # exception following. The backtrace in the view is generated from
       # reaching out to original_exception in the view.
       if error.is_a?(ActionView::Template::Error)
-        request.env['web_console.exception'] = error.original_exception
+        env['web_console.exception'] = error.original_exception
       end
     end
   end

web-console.gemspec

@@ -15,7 +15,7 @@ Gem::Specification.new do |s|
 
   s.required_ruby_version = '>= 2.2.2'
 
-  rails_version = ">= 4.0"
+  rails_version = ">= 4.2"
 
   s.add_dependency "railties",    rails_version
   s.add_dependency "activemodel", rails_version