Increase version number to 1.4.0 pre-release
The next (planned) version of cocotb will be 1.4.0. Increase the in-tree
version number to reflect that.
The naming is based on the rules outlined in
Fixes
# 1) we don't load dependencies by storing it in __init__.py
# 2) we can import it in setup.py for the same reason
# 3) we can import it into your module
-__version__ = '1.3.0'
+__version__ = '1.4.0.dev0'
