[btcsuite/btcd] 3fc244: txscript: Separate signing code.

[Dave Collins]

  Branch: refs/heads/master
  Home:   https://github.com/btcsuite/btcd
  Commit: 3fc244430933e69c079abd7c7f90d0be0d14fc6d
      
https://github.com/btcsuite/btcd/commit/3fc244430933e69c079abd7c7f90d0be0d14fc6d
  Author: Dave Collins <da...@conformal.com>
  Date:   2015-04-20 (Mon, 20 Apr 2015)

  Changed paths:
    M txscript/script.go
    M txscript/script_test.go
    A txscript/sign.go
    A txscript/sign_test.go

  Log Message:
  -----------
  txscript: Separate signing code.

This commit separate the transaction signing code into sign.go and the
related tests into sign_test.go.