Enable to change font

Default font `Impact.ttf` can't print non-alphanumeric characters
like Japanese, Chinese, and so on. So I want to set another one.

example)

    lolcommits --capture --test -m '笑' -f /Library/Fonts/Osaka.ttf

or

    export LOLCOMMITS_FONT="/Library/Fonts/Osaka.ttf"
    lolcommits --capture --test -m '笑'


---
`笑` means `lol` in Japanese :)