following #106, makes options.publicPath required via the API. alphabetizes optionsSchema (#1055)

* following #106, makes options.publicPath required via the API. alphabetizes optionsSchema

* fixing options validation tests

* reorg options schema

* refactoring options validation test to prevent needless duplication

Author: shellscape

lib/OptionsValidationError.js

@@ -2,7 +2,7 @@
 
 /* eslint no-param-reassign: 'off' */
 
-const optionsSchema = require('./optionsSchema.json');
+const optionsSchema = require('./schemas/options.json');
 
 const indent = (str, prefix, firstLine) => {
   if (firstLine) {

lib/Server.js

@@ -21,7 +21,7 @@ const spdy = require('spdy');
 const webpack = require('webpack');
 const webpackDevMiddleware = require('webpack-dev-middleware');
 const OptionsValidationError = require('./OptionsValidationError');
-const optionsSchema = require('./optionsSchema.json');
+const optionsSchema = require('./schemas/options.json');
 
 const clientStats = { errorDetails: false };
 const log = console.log; // eslint-disable-line no-console