added test vfsStreamWrapperFileTestCase::cannotRenameNotWritableFile() to show added check in vfsStreamWrapper::rename() (only writeable files are renameable/moveable)

Hello,

I'm really crossing fingers to myself that I don't missed reading something or understand the whole read/write/execute rights management wrong but I tried to implement a unittest for an [upcomming project](https://github.com/stevleibelt/incubator/blob/master/cli/generate/locator/test/Test/Net/Bazzline/Component/Locator/FileExistsStrategy/SuffixWithCurrentTimestampStrategyTest.php) and could not make it working as expected.

It is about renaming / moving a filename to an other filename while the file has no write permission.
My expectation is, that I get back an "false" when I try to do this, but I did not get it. I am expecting the same for trying to unlink a not writable file, but this is a story for another pull request if the current pull request leads to the "acknowledged" status :-).

Finally, i added ".idea" to the ".gitignore" file to prevent adding phpstorm/jetbrains ide files by mistake.

Greetings and thanks so far for this great testing tool!