Add -validate option to CLI

[jorgepedret]

The only way to validate that your template works in Harp Platform is to compile the template and see if it shows any errors.

It'd be better to have a validate option to take care of that for you.

$ harp -validate
OK

$ harp -validate
{
  "status": 400,
  "message": "Template Render Error",
  "dump": {
    "path": "/Users/jorge/Dropbox/harp.io/apps/jorge.harp.io/public/index.jade"
  }
}

$ harp
...
validate [path] checks if project compiles correctly
...

[sintaxi]

This is a good idea. There is some refactoring involved to make this work though. My not get to it right away.

[kennethormandy]

Another good use case came up for this in #93. The takeaway is that harp compile should run harp validate first. Right now, it will compile as much as it can to www until it hits an error. If you don’t see the error in the CLI, this makes it seem like the compile step was successful.