feat(launcher): Add support for maxSession

  - add support for maxSession and capability-specific specs
  - cleaned up launcher (refactored out taskScheduler.js)
  - (breaking change) changed the config to shard test files; also sharding is specific to capabilities now
    - Before: config.splitTestsBetweenCapabilities
    - Now: config.capabilities.shardTestFiles or config.multiCapabilities[index].shardTestFiles

Author: hankduan

lib/configParser.js

@@ -22,10 +22,6 @@ var ConfigParser = function() {
   // Default configuration.
   this.config_= {
     specs: [],
-    capabilities: {
-      browserName: 'chrome'
-    },
-    splitTestsBetweenCapabilities: false,
     multiCapabilities: [],
     rootElement: 'body',
     allScriptsTimeout: 11000,