chore: don't report pull request build status to SauceLabs

Closes #185
chore: use Firefox to capture test coverage

TravisCI has Firefox installed so we can use it in order
to capture tests coverage. Using Firefox makes it possible to
avoid installing PhantomJS which speeds up the npm install about
10 to 20 %.

Closes #186
build: properly detect pull requests
build: run tests on one android version only
chore: release 0.3.0
chore: start release 0.0.4-SNAPSHOT
build: use Travis-CI / SauceLab timeouts
fix issue #176

Closes #184
Fix error list display issue in the playground
chore: restore compiler's coverage reporting

Closes #192
build: switch to Linux-native connect tunnel

Closes #191