Fix issue where none root composer.json could be used by ArtifactRepository http://www.php.net/manual/en/ziparchive.locatename.php#85512
Improved variable name.
Package should have download options
Package options must be passed as argument to downloader
Package options should be dumped if exists
Package options must be a non mandatory array and should be loaded when
exists
Repository options must be replicated on package when dist file is under
repository base dir
Improved the handling of trunkPath

- $this->baseUrl is only used if $this->trunkPath === false, otherwise
we will use $this->baseUrl with $this->trunkPath.
- scanning through trunkPath will now look for composer.json file
instead of a path that matches $this->trunkPath, beacuse checking
against the latter failed with deeper trunkPaths
- $this->rootIdentifier is now 'trunk' no matter how deep
$this->trunkPath is (with deeper trunkPaths, the name became something
like "dev-trunk-devel-team-packages-package"
Fixed a coding style issue

Missing a space between if and (
Add a warning for unbound constraints in the validating loader

Closes #2165
Added a new FAQ entry about unbound version constraints
Add PSR-4 class loader. (tests needed)
PSR-4 class loader: Add getters for PSR-4 prefixes. Rename PSR-0 related attributes by appending *Psr0. Add more comments.
PSR-4 loader: Fix comments: PSR-0 related methods should have comments refering to PSR-0 and prefixes. PSR-4 related methods should have comments refering to PSR-4 and namespaces.
Further improve comments.
PSR-4 ClassLoader: Bug fix: PEAR-like path needs ".php" appended.
Add unit tests for ClassLoader, covering PSR-0 and PSR-4.
AutoloadGenerator to support PSR-4. Tests included.
Travis CI should use bin/composer and not system-wide Composer.
run system-wide composer install and THEN run bin/composer install