Jinja2 filesystem loading fixes, bugfixes, dot-env file management

Features:

• Bugfix #9
• Dot-env files support
• Bugfixes to alias groups support

Preparation for distribution mode - RKD_WHITELIST_GROUPS and RKD_ALIAS_GROUPS

Those features were made especially for RiotKit's Harbor project.

The Harbor would like to have tasks defined in :harbor group, but called directly without a group and having a custom binary harbor instead of rkd.

Example with standard rkd way: rkd :harbor:start
Example with distribution mode way: harbor :start

CI simplicity, lightweight dependencies, output buffering problems resolved

In this release following issues were resolved:

• #1
• #4
• #5

Feature release - Added JINJA2 support

v0.6.0.0b1

Feature: Add JINJA2 support

Clear changes to get_arg_or_env()

v0.5.0a1

Update docs

Environment variables definition order

v0.4.1.a2

Documentation for loading priority

Introduce subprocess compat mode

Output is corrupted or there is no output from a shell command executed inside of a task

The output capturing is under testing. The Python's subprocess module is skipping "sys.stdout" and "sys.stderr" by writing directly to /dev/stdout and /dev/stderr, which makes output capturing difficult.

Run rkd in compat mode to turn off output capturing from shell commands:

RKD_COMPAT_SUBPROCESS=true rkd :some-task-here

Introducing environment variables in YAML syntax

From now, following examples could be used at global YAML document level and per task.

env_files:
    - path/to/env/build-settings.env
environment:
    SOME: "thing"

Fixes and tests coverage

v0.3.1

Add good practices section

Testing release - v0.3 introduces YAML syntax

Added badge, quick start instruction