Add contributing guide
Release 0.6.0
Reminder to email mailing list when releasing.
Added tests for feature
Store the first env variable value overwritten
Support for append action + shortcuts
Added feature test for append feature
Changed implementation for set environment variable step
Added support for prepend
Merge branch 'feature/append_data_to_env_var' into integration/expand_path

Conflicts:
	features/command_environment_variables.feature
Fixed merge conflict