Fix edge case where code in multiple letter chapter is not found if the numeric part is over the end digit of the chapter.

[Pooppap]

I.e. if the ICD code is "C85.1", the previous version "in_chapter" function will return false on the "C00-D48" code block even though "C85.1" belong to that code block. This pull request proposes a fix to the issue while preserving the default behaviour for other non-edge cases.

[wbazant]

I did something slightly different, modifying the bounds check:

       if salpha == ealpha:
            return alpha == salpha and snumeric <= numeric <= enumeric
        else:
            return (salpha <= alpha < ealpha and snumeric <= numeric) or (salpha < alpha <= ealpha and numeric <= enumeric)

This was before I saw your solution to the same problem which the bounds to 100. Posted the whole code in #1 (comment).