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.
Add preFileDownload event on package.json fetch
don't require the error message have the first line of HTTP output in it
Merge pull request #2435 from ptarjan/master

don't require the error message have the first line of HTTP output in it
Cache in VersionConstraint
Merge pull request #2431 from bamarni/create-project-pretty-constraint

[CreateProject] allowed pretty constraint
Merge remote-tracking branch 'AlexeyKupershtokh/cache-version-constraint'
Rename a few things
Merge pull request #2434 from JJK801/extend-pre-file-download

Add preFileDownload event on packages.json fetch
Fix vcs repo constructor, fixes #2444
Fix pear ctor, refs #2444
Only replace version in Composer.php, fix user agent
Add test for RepositoryManager repo creation
Detect failed gethostbyname, refs #2449
Force unresolvable hosts through proxies, fixes #2449
Fix previous commit
Update deps
Fix exit codes, cc @tyrael
Use 'cache-files-ttl' for cache gc, fixes #2441

The configuration option 'cache-ttl' was used instead of 'cache-files-ttl' to determine
whether or not a cache gc should be performed.

* changed 'cache-ttl' to 'cache-files-ttl' to determine if a gc should be performed
* refactored FileDownloader to allow for easier testing
* added test to ensure that the gc is called with the proper config option