[conformal/btcjson] d1efe0: Add SetId() to Cmd along with tests.

[John C. Vernaleo]

  Branch: refs/heads/master
  Home:   https://github.com/conformal/btcjson
  Commit: d1efe0c10941ff3a994f35e0f15fee9e78c52e21
      
https://github.com/conformal/btcjson/commit/d1efe0c10941ff3a994f35e0f15fee9e78c52e21
  Author: John C. Vernaleo <j...@conformal.com>
  Date:   2014-01-08 (Wed, 08 Jan 2014)

  Changed paths:
    M jsoncmd.go
    M jsoncmd_test.go
    M test_coverage.txt

  Log Message:
  -----------
  Add SetId() to Cmd along with tests.