Add support for preserving Unicode characters in jsonpatch CLI

[Genzer]

If the JSON content contains some Unicode characters, the jsonpatch final output will encode the Unicode character using ASCII (i.e \u0394). This behaviour comes from the module json.dump() governed by a flag ensure_ascii1.

For example:

/* patch.json */
[{
  "op": "add",
  "path": "/SomeUnicodeSamples",
  "value": "𝒞𝘋𝙴𝓕ĢȞỈ𝕵 đ áê 🤩 äÄöÖüÜß"
}]

After applying the patch on an empty source file {}, this is the output:

{"SomeUnicodeSamples": "\ud835\udc9e\ud835\ude0b...\u00fc\u00dc\u00df"}

This commits add a flag -u|--preserve-unicode into the jsonpatch CLI to configure the behaviour of json.dump's ensure_ascii flag.

Using the --preserve-unicode flag, the final output will print the Unicode characters as-is without any encoding.

[coveralls]

Coverage remained the same at 65.846% when pulling 974d54f393de78ce21bee9897cee8f1ace5813ee on Genzer:master into dbea3db33298da4ec41197b07612c42580e132e4 on stefankoegl:master.

[stefankoegl]

Looks good, thanks :)