Refactor generateAlphabeticName for shrinking bundlesize
Refactor generateAlphabeticName for shrinking bundlesize

Rewrote generateAlphabeticName to compute its alphabet from
char codes. Also replace Math.floor with bitwise zeroing,
which works since it rounds by converting numbers to ints.

Tests cover this function and are still passing

styled-components/styled-components,styled-components/styled-components,styled-components/styled-components,JamieDixon/styled-components,JamieDixon/styled-components,JamieDixon/styled-components,css-components/styled-components