Version updates
Browsing to external URLs is prevented by default.

It is possible however to change that using the
CrawljaxConfigurationBuilder.

Also:

- Created an option to 'browse back' from the CrawlRulesBuilder
- Cleaned up unused method in CrawljaxConfiguration
Added DomUtilTest. Clean up imports.

Added a test that disproves #54.

Closes #54
Merge branch 'clean-up' into feature/328-do-not-open-external-url
Fixed serialize test
Merge pull request #335 from crawljax/feature/328-do-not-open-external-url

Feature/328 do not open external url