fix YouTube embeds in docs

[keikoro]

Fixes #304, renders #342 + #343 invalid.

[keikoro]

Replaces AS3 objects with iframes and gets rid of mixed content (http urls in https site).

[Zulko]

I'm not sure I understand what the problem is, the videos in the gallery work fine for me in Firefox and Chrome, is there a problem on some other browsers ? Are iframes the standard way of embedding youtube videos ?

[keikoro]

For me, the videos don't show in either browser + when opening the local versions of the files, I'm additionally experiencing the problem described by @COLABORATI in #304 (I'm prompted to download the files).

From the YouTube docs:

March 9, 2015

• The document has been updated to reflect the fact that YouTube <object> embeds, the YouTube Flash Player API and the YouTube JavaScript Player API have all been deprecated as of January 27, 2015. A deprecation warning appears in several sections of this document to help point readers to the IFrame Player API as an alternative.

[keikoro]

From Chrome's console:
Mixed Content: The page at 'https://zulko.github.io/moviepy/gallery.html' was loaded over HTTPS, but requested an insecure resource 'http://youtube.com/v/zJtWPFX2bA0?rel=0'. This request has been blocked; the content must be served over HTTPS.

I'm also getting warnings for images, but apparently browsers aren't as strict about those, so they still show up.

[keikoro]

I have no idea why the videos show for you, @Zulko, because they really shouldn't. Perhaps different security settings? Maybe you allowed mixed content for your docs at some point (if that is even an option)?

[keikoro]

When I try to access the http version of the docs, I'm actually also getting the download prompts (except Chrome doesn't just display the Download dialogue but pops up this message).

[keikoro]

(My browsers default to the secure version of the docs pages... as they should.)

[keikoro]

I'm also getting the download prompts on mobile. Have you tried opening the docs with a browser you haven't used for development? (I'm not sure if/how being logged in could additionally affect this.)

[keikoro]

Just leaving a note here that @Zulko approved this PR on Gitter.

[ghost]

Awesome!.. Lets merge this puppy then! :)