Bumped to v.3.1.4

gprMax/_version.py

@@ -1,4 +1,4 @@
 # This is where the version number is set and read by setup.py and conf.py (for the docs)
 
-__version__ = '3.1.3'
+__version__ = '3.1.4'
 codename = 'Big Smoke'