Patch for #6 - introducing the option to parse "strict"  or lenient.

As described in #6 making the internal parsing behavior more lenient (less strict) with regards to duplicate-key entries makes this library work more like the classic JSON.parse, and thus ensures less issues when people use it as a drop in replacement for that.

This patch still allows the old (fail-safe) parsing mode as an option. See Readme and test.js for usage example.

Tests and documentation (Readme) have been updated, as well as the package-minor-version number (per rules of semver.org)