Improve exception handling in parseYargs
Improve exception handling in parseYargs

The previous function did not handle exceptions thrown by callback (or
after callback is invoked) correctly and caused callback to be called a
second time.  Fix this.

Signed-off-by: Kevin Locke <ffb4761cba839470133bee36aeb139f58d7dbaa9@kevinlocke.name>

kevinoid/appveyor-status,kevinoid/git-branch-is,kevinoid/stream-compare,kevinoid/swagger-spec-validator,kevinoid/travis-status,kevinoid/promised-read,kevinoid/stream-compare,kevinoid/travis-status,kevinoid/node-project-template,kevinoid/git-branch-is,kevinoid/node-project-template,kevinoid/appveyor-status,kevinoid/promised-read,kevinoid/git-branch-is,kevinoid/stream-compare,kevinoid/node-project-template,kevinoid/swagger-spec-validator,kevinoid/promised-read,kevinoid/travis-status,kevinoid/swagger-spec-validator,kevinoid/appveyor-status