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 (
Resolves #2521. First and simple attempt to make a gzip downloader
There is no need in DIRECTORY_SEPARATOR since it Unix
Final fix. Preserve initial file name
Since there is no solution for non-unix (for now), remove the condition
Fix for #2739 (and #1755), added support for directory excludes in the .gitignore file like /directory or directory/
Fallback to gzip functions when on Windows
Updated the regexp and added more test cases.
Updated the regexp and added an other test case for sub dirs
Added `path` flag to show install path for installed packages
Type in comment
Skip test requiring mbstring when it's not installed
Merge remote-tracking branch 'sylvainfilteau/master'
Fix indenting, refs #2788
Merge pull request #2765 from neoascetic/gzip_downloader

Gzip downloader (resolves #2521)
Merge remote-tracking branch 'alebiavati/list-paths'
Added a failing test for #2626
fix "replace-alias.test" test
for AliasPackages check that the aliased package is white listed so that version constraints of AliasPackages are taken into account when computing package provisions