Fix: Adding check if char can be capitalized to new-cap (Fixes #940)

Fixes #940 

Adding a check to new new-cap options added in #904 to first see if the first character **can** be capitalized (in other words, if it's alphabetic). If it can't, then without this fix, one or the other of the rules' options must fail.

Note that the set of characters that can be capitalized is much larger than [A-Za-z].