Failing to delete bucket due to open object file handler

[sgerace]

While running some tests on a Windows machine, I kept getting Permission Denied errors when trying to delete a bucket shortly after (1) getting an object and then consequently (2) deleting the object. After some searching it looks like it is related to the NTFS pending deletion state (see this Stack Overflow post). After looking through the code (I'm no Ruby expert so feel free to correct me if I'm wrong), it looks like the issue might be originating from Line 78 in file_store.rb where the file descriptor to the metadata file isn't being opened in a block.

[sgerace]

I created pull request #61 with the suggested fix, which appears to take care of the issue on my development machine (its tough to know for sure since it was an intermittent issue, but I haven't been able to reproduce anymore).