chrome.app.window : remove dependence on `dart:html`

a step towards better testability; implementing the html.WindowBase
provides no benefit here
implement `chrome.runtime.getPlatformInfo` + test to fix #86

remove dependence on `dart:html` and the platform getters
Merge pull request #85 from rmsmith/html_independence

remove dependencies on `dart:html`
PlatformInfo : bug fix nacl_arch = nacl_arch
Merge pull request #87 from rmsmith/html_independence

PlatformInfo : bug fix nacl_arch = nacl_arch
remove one warning from permissions.dart
add a script for drone.io
Merge pull request #90 from dart-gde/drone

add a script for drone.io
Merge pull request #88 from dart-gde/permissions

remove one warning from permissions.dart
refactor the file system code to return our custom FileEntry objects instead of js.Proxy objects
removed unused imports
Merge pull request #91 from dart-gde/files-refactor

refactor the file system code to return our custom FileEntry objects ins...
move bot_io to a dev_dependency
move lib/src/chrome_launch.dart to tool/chrome_launch.dart
move to tool/src
Merge pull request #98 from dart-gde/chrome-launch

move bot_io to a dev_dependency