Added onBlur support, bug fixes and enhancements

[jamielesouef]

• Add the validation classes, allow date picker to show on the top or the bottom and fix related look and feel
• Default text should be a placeholder rather than a input value
• Add today button for date picker(mode='date')
• Remove unused code
• Fix a bug where invalid initial input breaks the datepicker
• Calcuate the position when switching from date to year or month view
• Add different class name for month/year/time view
• Added support for onBlur
• Fixed markdown issues in README.md

[chollier]

Could you please not include dist and not bump version, I do that on the release step and sometimes bundle updates

[jamielesouef]

Amended