Support 4(+) Character Keywords

[steele232]

Right now, the convert function only supports 3-Character keywords.

We just got a new keyword added to the mapping with 4 characters, but it won't work properly until the searchAndReplaceAll function is able to search for keyword strings with 4 characters in them.

This could use a more elegant solution than adding a variable named "fourRunes" following the pattern of the earlier code (Look at lines 261-283 in convertAll.go). Presumably, the keywords will be short and I shouldn't need to add support for much larger keywords, BUT it still is a bit of a drag to be manually duplicating code to support larger and larger keywords. (Very theoretical: Think about if this repo was forked and used for a language other than Chinese, they would probably need to use many more characters than just 3 or 4!) I think I will try and make a little more elegant solution to this...