[20160614203313] Convox Start Improvements

@awsmsrc fixed a few good bugs that have been reported in the convox start development tool.

The docker-compose.yml file has improved parsing and validation for labels like convox.cron. And .dockerignore is handled better in development file syncing and uploading during convox build.

This update also includes a security enhancement where the convox client now validates the console.convox.com cert.

convox update to get the latest goodies.

See the following PRs for more info:

  • #763 validate cron labels
  • #762 take .dockerignore into account when using sync
  • #757 use docker archiving tool
  • #742 dont report bad yaml errors on start
  • #753 always verify the certificate for console.convox.com