"Content-Disposition" is stored directly in the headers array

Since the function now uses "JHttpFactory::getHttp()" instead of "stream_get_meta_data", the "Content-Dispositon" data is now stored directly in the $response->headers['Content-Disposition'] instead of $response->headers['wrapper_data']['Content-Disposition'].

Currently in Joomla 3.0.2, you can't install extensions directly from an URL if the URL points to a dynamic created link (like in Akeeba Release System or CTransifex). This is because it doesn't detect a valid filename.
This commit fixes this.
Use 'load_language' property as a flag to load the language files so that the constructor doesn't need to be overridden for this purpose.
Use camel case
Change to 'autoloadLanguage'
Add token based authentication to JGithub
Add JGithubUsers
Merge pull request #1813 from elkuku/github-users

Add JGithubUsers
Fix unit tests for JGithubUsers (Ref #1813)
Merge pull request #1814 from elkuku/github-users

Fix unit tests for JGithubUsers (Ref #1813)
Merge pull request #1812 from elkuku/github-oauth

Add token based authentication to JGithub
Merge pull request #1734 from okonomiyaki3000/JPlugin-load_language

Use 'load_language' property as a flag to load the language files
Merge pull request #1795 from Bakual/patch-1

Fixing extension install from dynamic URLs