Calendar page - Bootstrap/Responsive Design

# Description/Steps to reproduce
Based on https://github.com/ChickenKyiv/frontend/issues/8#issuecomment-398451037
> This is really main problem.
I don't know how to do responsive on React.
I only know about bootstrap grid system a little.
I really hope to learn responsive design

@icreamsoft Let's talk here about how we'll make it mobile ready.
Right now this task only for our plans. We didn't start to work on it while we don't have a propper plan.

# Expected result

# Additional information

Start with the Calendar page and the referenced frontend issue #8 discussion about making the page mobile-ready with React and the Bootstrap grid system. The issue says work has not started and that a proper plan is still needed; done would require an agreed responsive-design plan before implementation begins.

Written by the indexing model from the issue text.