validate logger level

[ycpatel813]

Issue Description

logger: new winston.Logger({
    level: 'debgu',
    exitOnError: false,
    transports: [
      new (winston.transports.Console)({
        prettyPrint: true,
        colorize: true
      })
    ]
  })

by mistake i wrote dubgu in logger level after that trails app did not start and did not respose any error message
so it is useful that trails validate logger level

Environment

• node version: v4.4.4
• trails version: ^1.0.0-beta-1
• operating system: Window 7

[jaumard]

We have to find a way to test/detect this... Because we can't validate the logger level because the logger can be any logger (not Winston) and then level will be not defined.

[tjwebb]

Yea, this is hard. The level is being sent into Winston as an argument, and isn't directly accessible to the application.

[tjwebb]

Continued in #261.