chore: Simplify travis CI
feat(targets): Add mode options for yargs
feat(mux): Add mode to constant
feat(mux): Remove cleaning of generated tasks

Removing the generated tasks creates an issue when running as a child of gulp task. The callback seems to never call the parent task
feat(targets): Add askForMultipleTargets and askForSingleTarget
fix(mux): resolveConstants now return correct type for values
chore: Clean package.json
Merge pull request #7 from thaiat/fix-issues