chore: git ignore /.pub
fix(components): the content tag duplicates elements

Closes #1422
chore(travis): skip dart version 1.7.0-dev.1.0 / dartbug 20896
chore(travis): remove dart version blacklist for 1.6.0-dev.8.0

Closes #1350
chore(travis): remove blacklist for g3v1x with sdk 1.5.8
squash! wip
squash! wip
update e2e tests to run saucelabs as well.