fixed typo: notbook-splitter -> notebook splitter

README.md

@@ -34,7 +34,7 @@ Since Notebooks are just JSON, I wrote a small parser in Python which suits my n
 It works by providing *tags* of cells to `keep` and *tags* of cells to `remove`. For instance,
 
 ```bash
-notbook-splitter $< --keep task --keep solution --remove nopresentation
+notebook-splitter $< --keep task --keep solution --remove nopresentation
 ```
 
 would look into Notebook cells and keep those which are *tagged* `task` or `solution` and remove those which are tagged `nopresentation`. One special tag for removal exists, `all`, which removes everything except what's marked to keep. A tag in the sense used here is a value to a JSON key in the cell's metadata, which is per default `"exercise"` (but can be selected via `--basekey`. Example: