Make it clear that compressed NTFS is not supported (#69)

* Make it clear that compressed NTFS is not supported

See #67 (comment)

* Files can be compressed or not, not the whole filesystem

* Added sentence on lacking documentation for compressed files

README.md

@@ -56,6 +56,10 @@ and export the contents of a partition in CSV or
 [body file](http://wiki.sleuthkit.org/index.php?title=Body_file) format. These
 are exported in the directory specified by `-o` (or `recuperabit_output`).
 
+### Limitation
+
+Currently RecuperaBit does not work with compressed files on an NTFS filesystem. If you have deep knowledge of the inner workings of file compression on NTFS filesystem, your help would be much appreciated, as available documentation is quite sparse on the topic.
+
 ### Pypy
 
 RecuperaBit can be run with the standard cPython implementation, however speed