add support for date formatting

[mderazon]

using Date.toISOString()

Output example:

{
    "time": "2016-06-22T12:30:51.210Z",
}

[mderazon]

I guess i'll leave this open until it's published to npm

@mafintosh can you please close this when you do ?

[mafintosh]

published and added @Kikobeats to npm. thanks

[Kikobeats]

@mafintosh I see me as collaborator on npm registry but no permissions for publish

❯ npm publish
npm ERR! publish Failed PUT 403
npm ERR! Darwin 16.1.0
npm ERR! argv "/usr/local/bin/iojs" "/usr/local/bin/npm" "publish"
npm ERR! node v7.2.0
npm ERR! npm  v3.10.9
npm ERR! code E403

npm ERR! "You cannot publish over the previously published version 1.1.0." : json-markup
npm ERR!
npm ERR! If you need help, you may report this error at:
npm ERR!     <https://github.com/npm/npm/issues>

npm ERR! Please include the following file with any support request:
npm ERR!     /Users/josefranciscoverdugambin/Projects/json-markup/npm-debug.log

[mafintosh]

@Kikobeats that's because I published it for you already :) should work for future releases

[Kikobeats]

ops, true! thanks 👍