BF,RF: Fix a few bugs, adjust `evalHeader` routine

Adjusted the evalHeader routine - now it compares dim and pixdim for all valid dimensions by default. The alldims parameter has been replaced with a ndims parameter, allowing the number of dimensions to be set (e.g. when you only want to compare the first three dimensions).

pyfeeds/tests/__init__.py

@@ -9,8 +9,6 @@
 import os
 import sys
 import os.path as op
-import contextlib
-import tempfile
 
 from io import StringIO
 
@@ -61,17 +59,6 @@ class CaptureStdout(object):
         return self.__mock_stderr.read()
 
 
-@contextlib.contextmanager
-def tempdir():
-    prevdir = os.getcwd()
-    with tempfile.TemporaryDirectory() as td:
-        try:
-            os.chdir(td)
-            yield td
-        finally:
-            os.chdir(prevdir)
-
-
 def makepaths(paths):
     for path in paths:
         dirname = op.dirname(path)