Utility to generate a JSON object from a tabulated file

Summary:
This allows to copy/paste from Excel, LibreCalc, FramaCalc, etc.
into a temporary file, then convert this key\tvalue file into a
proper JSON object representation.

Sample input:

fr\tprénom
en\tgiven name

Sample output:

{
    "fr": "prénom",
    "en": "given name"
}

Test Plan: Use jsonlint to validate JSON is well formed.

Reviewers: Ash-Crow

Differential Revision: http://devcentral.nasqueron.org/D433