Merge PR's , bump version to 2.4.0

Author: sanjay

CHANGELOG.rst

@@ -1,3 +1,9 @@
+Version 2.4.0
+----------------------------------------------------------
+* Support async moduls tls server/client
+* Add local echo option
+* Add exponential backoffs on retries.
+
 Version 2.3.0
 -----------------------------------------------------------
 * Support Modbus TLS (client / server)

pymodbus/version.py

@@ -41,7 +41,7 @@ def __str__(self):
         return '[%s, version %s]' % (self.package, self.short())
 
 
-version = Version('pymodbus', 2, 3, 0)
+version = Version('pymodbus', 2, 4, 0)
 
 
 version.__name__ = 'pymodbus'  # fix epydoc error