Supported Hex string: 'x'

[Jinjiang]

1. Added Hex string supporting for a little requirement from my job works. I use a temp format name: x, because I found this format in PHP is H but this program have had H for unsigned short. I also write a test script in ./test/hexstring.js
2. Updated the dev dependencies versions The package should doesn't work well in the previous version. So I updated the package info.

Hope to be useful.

Thanks.

[haosdent]

+1 But "This pull request contains merge conflicts that must be resolved.", could you rebase it @Jinjiang