Updated beta version to 3.0.0b4

docs/source/conf.py

@@ -69,7 +69,7 @@ author = 'Craig Warren and Antonis Giannopoulos'
 # The short X.Y version.
 # Read version number from gprMax/gprMax.py
 #version = re.search('^__version__\s*=\s*\'(.*)\'', open('../../gprMax/gprMax.py').read(), re.M).group(1)
-version = '3.0.0b3'
+version = '3.0.0b4'
 # The full version, including alpha/beta/rc tags.
 release = version + '(Bowmore)'