Remove Unicode symbols from documentation

[jvoigtlaender]

... because they kill people in situations like this.

[jvoigtlaender]

@evancz, this presence of Unicode symbols in the core documentation (and the inability of at least some elm-make binaries, under some circumstances, to read those symbols in) is hurting people continuously. For no good reason, it seems. (Or are those symbols that important to have in the documentation?)

For yet another incident like that, see elm-lang/elm-make#33 (comment).

[jvoigtlaender]

@evancz, this presence of Unicode symbols in the core documentation (and the inability of at least some elm-make binaries, under some circumstances, to read those symbols in) is hurting people continuously. For no good reason, it seems. (Or are those symbols that important to have in the documentation?)

For yet another incident like that, see elm-lang/elm-make#33 (comment).