Fix spec typos for "minimun"

https://github.com/rubinius/rubinius/pull/2576#discussion_r5997958
Fix spec typos for "missing a/an"

https://github.com/rubinius/rubinius/pull/2576#discussion_r5998046
https://github.com/rubinius/rubinius/pull/2576#discussion_r5998001
Fix spec typos

"sets and get": https://github.com/rubinius/rubinius/pull/2576#discussion_r5997995

"HTMl": https://github.com/rubinius/rubinius/pull/2576#discussion_r5998021

"a/an with plural": https://github.com/rubinius/rubinius/pull/2576#discussion_r5997976
Improve a BigDecimal#to_s spec description

https://github.com/rubinius/rubinius/pull/2576#discussion_r5998018
Update failing spec tags