REL: go back to unversioned pycifrw in setup.py.

PyCifRW 4.3.0 works with latest releases of Python 2.7.
This reverts commit 51d6f09.

Author: pavoljuhas

setup.py

@@ -84,7 +84,7 @@ def getversioncfg():
     include_package_data = True,
     zip_safe = False,
     install_requires = [
-        'pycifrw != 4.3.0',
+        'pycifrw',
     ],
 
     author = 'Simon J.L. Billinge group',