parent expression hack - notify when it will not work

[shaunlebron]

Plugins may use a hack to quickly locate top-level expressions—by finding lines starting with (, [, or {.

We can return parentExpressionHack false if:

• top-level expression starts a x > 0
• line inside a string starts with (, {, or {

[shaunlebron]

parens is an array of top-level expressions {lineNo, x, closer, children} that is returned if returnParens is enabled.

added: https://github.com/shaunlebron/parinfer/commit/e48455d85bcdb6ad50cbc1f56906e276b2d0ae6e

[shaunlebron]

i'll leave this open since it's not a full solution