Implement stream management and streaming concept (see #3)
Add stream observers.
Update Stream::open and Stream::close have to return bool.
Fix missing use in Stream file.
Add StreamMode::getMode().
Fix incorrect usage of object in StreamWrapper.
Add stream uri to FilesystemConfig.
Add stream uri implementation to AbstractFilesystemConfig.
Fix code style.
Add stream wrapper register on create to AbstractFilesystem.
Add AbstractSimpleFilesystem::getURLOf().
Add LocalFilesystem::getStreamOf().
Use internal stream in LocalFilesystem::open() instead of native stream.
Correct cleanup in LocalFilesystemTestEnvironment.
Add BuildInStream implementation.
Add first draft of abstract stream test class.
Add local filesystem stream test.
Use phpunit loaded by composer for testing.
Add missing class StreamWrapperNotRegisteredException.
Add phpunit.xml to .gitignore.