CHANGELOG does not reflect changes for 0.6.0

[TALlama]

Please help us out by letting us know what changed. Looking at the diff, my rookie eyes see:

• Updated to latest version of pygments
• Allow setting a custom timeout by setting ENV['MENTOS_TIMEOUT']
• Cache lexers for better performance
• Fixed an issue where TOML might not be recognized properly
• Made it clear what license the project uses

[parkr]

@TALlama Can you submit a PR? They're easier to deal with.