Removed hyperspy from [all] installations.

Hyperspy depends on traits which doesn't have wheels on PyPI,
so they would need to be compiled during installation
(needs 4.3GB of stuff...)

setup.cfg

@@ -61,10 +61,11 @@ fftw =
 colors =
     cmocean
 all =
-    hyperspy
     pyfftw
     cmocean
-
+# TODO: pip install .[io] is not working because hyperspy depends on trait which has no wheels on PyPI at the moment...
+# TODO: See https://github.com/hyperspy/hyperspy/issues/2315 and https://github.com/enthought/traits/issues/357
+# TODO: Add hyperspy back as soon (if?) this is resolved... Until then: install hyperspy with conda!
 
 # CONFIGURATION FOR TESTING: