regular expression support

[suntong]

Following up on jmespath/jmespath.jep#23

different programming languages have different regular expression implementations

Fine, but how about providing a regular expressions function among the Built-in Functions.
The regular expressions will be Go specific, but that's much better than not having any regular expression support, for jp at least.

[suntong]

I don't mind giving it a try if it can be accepted.

[suntong]

Fixed in #65

    {
      "expression": "matches('This and these', 't(his|h[eo]se)')",
      "result": true
    },
    {
      "expression": "matches('Those people', 't(his|h[eo]se)')",
      "result": false
    },
    {
      "expression": "matches('THOSE people', '(?i)t(his|h[eo]se)')",
      "result": true
    },

[suntong]

jp v0.2.2 released -- added matches for regular expression support. See
https://github.com/go-jsonfile/jp/releases/tag/v0.2.2