Regex parser for name should not include '-' character for elm 0.18

The current definition believes that minus character can be part of variable names, while the elm-repl for 0.18.0 does not aggree
https://github.com/Bogdanp/elm-ast/blob/8.0.7/src/Ast/Helpers.elm#L89
```elm
name : Parser s Char -> Parser s String
name p =
String.cons <$> p <*> regex "[a-zA-Z0-9-_]*"
```
Explanation:
```
/[a-zA-Z0-9-_]*/g
Match a single character present in the list below [a-zA-Z0-9-_]*
* Quantifier — Matches between zero and unlimited times, as many times as possible, giving back as needed (greedy)
a-z a single character in the range between a (index 97) and z (index 122) (case sensitive)
A-Z a single character in the range between A (index 65) and Z (index 90) (case sensitive)
0-9 a single character in the range between 0 (index 48) and 9 (index 57) (case sensitive)
-_ matches a single character in the list -_ (case sensitive)
```

I believe changing the regex to `"[a-zA-Z0-9_]*"` would work. This is such a small change that it could be better done straight through the web interface by a contributor.