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
Merge pull request #2472 from vuhl/master

Added some error handling and error messages for common errors using Perforce driver
Check exclude from downloaded composer.json
Merge pull request #2482 from oziks/fix-composer-archive-property

Check exclude from downloaded composer.json
Check exception code only if class ZipArchive exists

If is for example exception throwed when downloading tar archive on system without installed zip extension, PHP hangs on fatal error " Class 'ZipArchive' not found".
Merge pull request #2483 from JakubOnderka/patch-2

Check exception code only if class ZipArchive exists
Detect ~> misuse and suggest fix, fixes #2476
Fix error on check exclude from download composer.json
Add psr-4 stuff in a few more places.
Validation to make the combination of target-dir with psr-4 illegal.
Skip aliases packages when looking for plugins.
Ensure detected extensions have valid package names