fix(test): support firefox, safari and opera as test browser

Add karma plugins to launch these browsers

Closes #19
fix(test): update the karma-junit-reporter plugin from 0.1.0 to 0.2.1
fix(test): run tests with no browser started automatically

Implements Solution 2: Remove PhantomJS from system.config.js

Closes #18
fix(config): add caching for assembled build config

Add simple caching with a variable.

Closes #17
bumps version to 0.3.2
doc(changelog): update changelog for 0.3.2
Merge branch 'hotfix/0.3.2'