Gemfile was updated.

Please don't change ruby and rails version.

Steps to set up environment:

1. a new c9 environment for ruby 2.4.1.

2. git clone this repository after fork.

3. Please input following commend to solve problems from pq 0.20.0.

commend: for pq 0.20.0 do not work:

sudo yum install libpqxx-devel

4. If you have any question, please contact me.