Add the ability to do regex expressions

[djgilcrease]

I needed the ability to do a regex search on the value of some fields, so I added it

[coveralls]

Coverage increased (+0.03%) to 90.79% when pulling 36af214 on Digitalxero:regex-expr into d081f83 on danvk:master.

[danvk]

Is this actually a CSS4 thing? Do you have a link to a spec?

[djgilcrease]

Not it is not. They do have the ~= attribute selector, but they have it parsing a whitespace separated list for a word match.

[danvk]

I can definitely see this as being useful, but I'm reluctant to include a syntax that's not related to any CSS spec, let alone the original jsonselect spec.

[djgilcrease]

According to the jsonselect website

"JSONSelect Level 3 adds constructs which do not necessarily have a direct analog in CSS, and are added to increase the power and convenience of the selector language. These include aliases, wholly new pseudo class functions, and more blue sky dreaming."

http://jsonselect.org/#docs

So adding a new pseudo class is within the spec