Use better characters for "jumping over" branches

[rbong]

Right now git-forest uses triple bar ("≡") (unicde 2261) to display "jumping" over branches.

I have been exploring other characters, and it may show up more naturally if you use upper half circle ("◠") (unicode 25e0) followed by box drawing right line ("╶") (unicode 2576) or horizontal line ("─") (unicode 2500).

On my terminal, the half circle covers 1.5 characters, but in other fonts it covers only 1. One of these should show up correctly in GitHub:

─◠╶
─◠─

This is more in line with how other branch viewers show skipping over branches, and in my opinion, looks nice, but the half-circle may look a little small using some fonts. Here's how it looks in my terminal (not using git-forest).

[rbong]

Update: with a better font, looks good.