You can continue to build the project on 1.0 while trying 2.0.
Create a new branch and remove
circle.yml config file and replace it with a
.circleci/config.yml file with 2.0 config.
Then all builds on other branches will run with 1.0 while the test branch will build on 2.0 while you try out the config. The docs have migration information: https://circleci.com/docs/2.0/faq/