Kola v0.1.0b5

Fix severial bugs and add environment support in KoiLang class

Kola v0.1.0b4

fix(parser): add currect traceback to CommandError

Now you can see traceback to kola file in KoiLangCommandError.
Fix command field inherit.
Change KoiLang.parse_file and KoiLang.parse_string.

Kola v0.1.0b3

Fix bugs in v0.1.0v1

Kola v0.1.0b1

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