API Defaulting composer core dependencies to to @stable

Required to ensure correct operation of
"composer create-project silverstripe/installer my-path 2.4.10"
(checkout with tags).
Removed @stable markers from 2.4 dev branch
Updated github path
case insensitive the assets/ allowed extensions for Apache
Merge pull request #40 from NightJar/hackfest_may_2013

case insensitive the assets/ allowed extensions for Apache
HTML5 video file types.
Merge pull request #41 from uniun/HTML5-video-file-types

HTML5 video file types.
NEW: Added post-install and post-update dev/build call.

With this change, composer will automatically call dev/build after an update or install
command.  The main reason that this is 3.1-only is that previous releases would have
necessitated the use of 'sudo -u www-data', which is too environment-specific.

One thing that this may cause problems with is 'composer create-project' in an environment
without a _ss_environment file.  It will call dev/build, and dev/build will throw an
error.  That should be fixed in a subsequent commit.
git commit -m "FIX: Move install composer.json to use self.version.

Now that Composer has been fixed, self.version can be used as a dependency for framework
and cms in installer.  This simplifies our composer.json, and meanst that we can commit
composer.lock into the repo, as required.  An annoying piece of our release process has
been solved!
Merge branch '3.0' into 3.1
Merge pull request #42 from sminnee/composer-post-install

NEW: Added post-install and post-update dev/build call.
Revert composer.lock addition, unclear usage, breaks builds

Partially reverts e9f13512dcd7ec6cf6e916c07ce0375a62c34c13

This caused two issues in Travis builds:
 * CMS builds were using
outdated framework dependencies. Example: https://travis-ci.org/silverstripe/silverstripe-cms/jobs/7718686
 * Modules weren't building
at all because the info in the lock file overwrote the custom
composer.json. Example: https://travis-ci.org/silverstripe/silverstripe-translatable/jobs/7726954

In addition, I don't agree with having lock files on release branches
(as opposed to tags), since it forces us to permantently update lock
files or work with stale dependencies even when on branches
(most likely not the developers intention).
Merge remote-tracking branch 'origin/3.0' into 3.1
Block access to .yaml files as well as .yml
Merge remote-tracking branch 'origin/3.0' into 3.1
Fixing regression in composer post scripts

Fixes regression on Windows where composer update and composer install because the path is hardcoded to only work on *nix systems.
Merge pull request #44 from silverstripe/remove_post_scripts

Fixing regression in composer post scripts
FIX Include flushtoken when install redirects to successfullyinstalled
Merge pull request #47 from hafriedlander/fix/flush_24

FIX Include flushtoken when install redirects to successfullyinstalled
Merge remote-tracking branch 'origin/2.4' into 3.0