Hotfix for Windows OS support

This MR provides a hotfix for #120 by making import fcntl optional in Util.py, so that code which relies on Util.py can load successfully on Windows.

With this fix applied, if a Windows user tries to call util.write_state_file or util.read_state_file it will fail with a warning without blocking further execution. This should only affect Windows users that run MiniSeedFactory with convert_channels ~= None (unlikely!). Even if they do try this it should run successfully but without any reading or writing of state files.

I tested this fix on a Windows installation of Python and appears to work.

geomagio/Util.py

@@ -279,6 +279,7 @@ def write_state_file(filename, data, directory=None, encoder=None):
                 print(
                     f"The fcntl module is not supported in Windows. Reading/writing state files will not work: {e}"
                 )
+                pass
             except IOError as e:
                 print(f"Error locking or writing to file: {e}")
                 raise
@@ -290,9 +291,6 @@ def write_state_file(filename, data, directory=None, encoder=None):
         raise
 
 
-write_state_file("testjunkfile", "dataaaaa", "/home/bgeels/")
-
-
 def read_state_file(filename, directory=None, decoder=None):
     """
     Reads data from a state file in a thread-safe manner.