button: block description
Merge pull request #467 from bem/issues/429@v2

button: block description. Closes#429
button: description + fix typo
Merge pull request #490 from bem/issues/429@v2-a

button: description + fix typo
attach: block description
Merge pull request #468 from bem/issues/431@v2

attach: block description
Building docs with ENB