Merge pull request #1103 from jacobdr/1102-docs-for-intemporary-directory

DOC: Update documentation for InTemporaryDirectory to note it as not thread-safe

Closes #1102

Author: matthew-brett

nibabel/tmpdirs.py

@@ -51,6 +51,12 @@ def __exit__(self, exc, value, tb):
 class InTemporaryDirectory(TemporaryDirectory):
     """ Create, return, and change directory to a temporary directory
 
+    Notes
+    ------
+    As its name suggests, the class temporarily changes the working
+    directory of the Python process, and this is not thread-safe.  We suggest
+    using it only for tests.
+
     Examples
     --------
     >>> import os