Update setup.py - minimal lxml instead of pinned.

Author: phanak-sap

setup.py

@@ -40,7 +40,7 @@ def _read(name):
     zip_safe=False,
     install_requires=[
         "enum34>=1.0.4",
-        "lxml==3.7.3",
+        "lxml>=3.7.3",
     ],
     extras_require={
     },