Changes to travis config to remove sudo requirement and to add support for pub run test -p chrome
Changes to travis config to remove sudo requirement and to add support for
pub run test -p chrome

DrMarcII/webdriver.dart,google/webdriver.dart,DrMarcII/webdriver.dart,bwu-dart-contributing/webdriver.dart,bwu-dart-contributing/webdriver.dart,google/webdriver.dart,google/webdriver.dart,staats-google/webdriver.dart,staats-google/webdriver.dart,bwu-dart-contributing/webdriver.dart,DrMarcII/webdriver.dart,staats-google/webdriver.dart,staats-google/webdriver.dart,DrMarcII/webdriver.dart,bwu-dart-contributing/webdriver.dart