Modify strictness

[bertothunder]

The 'strict' parameter in parser and M3U8 class has little effect, with very bold strictness checking being applied while parsing the input M3U8 manifest.

How 'strict' must the strict parameter force the parser to be? I can think about several levels of strictness checking:

• Check deprecated or non-supported tags based on version.
• Check for tag's format and mandatory parameters.
• Check for overall M3U8 format: EXTM3U tag is mandatory, never checked to be present.

More than an issue, this intends to be a question to open a debate about the model to be implemented. Ideas?