ecell4 1.2.0 does not work with ecell4_base 2.0.5

[kozo2]

This is due to forgetting to update setup.py
We need to increase the version of ecell4_base in the ecell4 setup.py from 2.0.5 to 2.1.0.

[pcarmich]

Had issue with version dependencies as well, when running colab for the first time says "ERROR: Cannot install ecell4==1.0.0, ecell4==1.1.1, ecell4==1.1.2 and ecell4==1.2.1 because these package versions have conflicting dependencies." The conflict might be with ecell4_base?