:scissors: whitespace
Add an opt-in progress bar to show XHR loading status
Guard against calling #done when there's no value
Force repaint so IE reflects opacity change
Add a slow response for testing / visualizing the progress bar
Fix ::before syntax
Document progress bar
Merge pull request #415 from javan/progress-bar

Progress bar
Clarify "the html element" for progress bars

When I first read "the progress bar is implemented on the html element" I thought, "What html element?" I think this change makes it a bit clearer that it's the actually the `<html>` tag
Merge pull request #417 from smidwap/patch-1

Clarify "the html element" for progress bars
Note that the progress bar will be on by default from Turbolinks 3.0
Release new version with the progress bar feature
Reflect the redirected url before actually changing the page, so page:change listeners get to see the final URL, rather than the before-redirect URL
Bump for bug fix
Give progress bar a high z-index value by default
Use document.documentElement.cloneNode() when parsing new documents

This lets browsers correctly choose which image to use when using
resolution independent html features such as:

    <img src="image.png" srcset="image@2x.png 2x, image@3x.png 3x">

Without this fix, in many browsers pages loaded through turbolinks
will never show the higher resolution alternatives even when viewed
on retina-like displays.

The reason for this is that browsers based on the latest versions
of both Blink and WebKit (and maybe other engines too) set the
device pixel ratio (DPR) of detached DocumentElements to 1.0. They
only gain a correct DPR when displayed in a browser window, by which
time the choice between multiple resolution images has already been
made.

This affects all existing document creation methods, as they all create
new DocumentElements. Using cloneNode() instead on the existing document
creates a new DocumentElement that inherits its DPR from the currently
displayed page, thereby allowing the correct images to be chosen.
Merge pull request #423 from mattbrictson/patch-1

Give progress bar a high z-index value by default
Fix back button broken on redirect
Merge pull request #430 from phallguy/master

Fix back button broken on redirect
Merge pull request #425 from tomafro/use-clone-node-to-enable-resolution-independence

Use document.documentElement.cloneNode() when parsing to fix resolution independence