0.2.0 new flag `--skip-existed` & check for already existed variables & connections

1. Added check for variables - now if variable already exists on server Airflow Helper will raise error if you tries to overwrite it from the config.
   To overwrite existed Variables, Connections, Pools - use flag '--overwrite' or argument with same name, if you use Airflow Helper from Python.

2. Added flag --skip-existed to avoid raise error if variables/connections/pools exists already on Airflow Server - it will just add new one from config file.

0.1.2 Small fix release

0.1.2

1. Should not fail if some sections from the config do not exist.

0.1.0 Airflow Helper initial release

**Airflow Helper** is a tool that currently allows setting up Airflow Variables, Connections, and Pools from a YAML configuration file. Support yaml inheritance & can obtain all settings from existed Airflow Server!

You can use it as command line tool, from docker container (https://hub.docker.com/repository/docker/xnuinside/airflow-helper/) or in pure Python code.

Enjoy!