Failure Reporters

• Add reporters: quiet reporter prints the copy command and
  diff reporters open an external diff tool.
• Extensive list of predefined diff tools for approval_first_working_diff.
• Verify without cmocka using plain assert.
• Release binaries for Windows x86 and Linux x86, too.

Initial Release

• Verify using verify_txt() and verify_xml() macros with cmocka.
• Format XML before verification, so approved file is readable.
• Release binaries for Windows x64 and Linux x64.