Minor change to README to remove closing the FileSystem from the example.
Minor change to README to remove closing the FileSystem from the example.

Since closing the FileSystem is not so important now that it can be GCed regardless.
Also adds a small reference to Windows-style file systems and a disclaimer about the
behavior's ability to exactly match that of any specific file system.
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Created by MOE: http://code.google.com/p/moe-java
MOE_MIGRATED_REVID=67631673

rasheedamir/jimfs,akkinenirajesh/jimfs,wrmsr/jimfs,rasheedamir/jimfs,thejavamonk/jimfs,yaochang/jimfs,google/jimfs,szpak/jimfs,wrmsr/jimfs,akkinenirajesh/jimfs,szpak/jimfs,google/jimfs,yaochang/jimfs