best μ and σ

See #74, release log:

• 2866d0d by @yegor256: #74 or
• c9d1b02 by @yegor256: #74 div
• 2d0b4dc by @yegor256: #74 typo
• 77ab073 by @yegor256: #74 mu and sigma

Released by Rultor 1.66.3, see build log