Documentation and Feature Update

• add a example script (example.py) with all functions
• add yaml-output support

with OutputFormat('yaml'):
    print_table('id name'.split(), [{'id': 1, 'name': 'Test #1'}, {'id': 2, 'name': 'Test #2'}])

id: 1
name: 'Test #1'
---
id: 2
name: 'Test #2'

• add warning(msg) and ok(msg) for class Action

with Action('Calc 1 + 1..') as act:
    act.ok(1+1)

with Action('Oh, I make a warning..') as act:
    act.warning('work is complicated')

Calc 1 + 1.. 2
Oh, I make a warning.. work is complicated

• add default for choice

state = choice('Please select the state of your work', ['Done', 'In Progress', 'unknown', 'lost'], default='lost'

Please select the state of your work
1) Done
2) In Progress
3) unknown
4) lost
Please select (1-4) [4]: