Moved lxml to testing dependency

Author: chapinb

setup.py

@@ -24,7 +24,6 @@
         install_requires=[
             'six',
             'hexdump==3.3',
-            'lxml==4.6.3',
 
             # pin deps for python 2, see #67
             'more_itertools==5.0.0',
@@ -37,6 +36,7 @@
             "test": [
                 'pytest-cov==2.11.1',
                 'pytest==4.6.11',
+                'lxml==4.6.3',
             ]
         },
         scripts=['scripts/evtx_dump.py',