Use Java 6 compatible symbol regex pattern

The `isAlphabetic` method only appears in Java 7. The Letter Unicode
category (L) should hopefully be enough. The only case I can think
that's left out is the 'Number, Letter' category which has things like
Roman Numerals. I think that's fine to leave out.
Specify file.encoding as UTF-8 in Lein project

Under OS X, I was presented with the following:

    BODOL version 0.0.0
    You are in a maze of twisty little passages, all alike.
    ??

I then tried to input:

    (ƒ triplet a b c -> (list a b c))

It looked right in the terminal but didn't parse correct. Specifying
the Java file encoding to be UTF-8 fixed everything.