Fix graphme_substr for PHP >= 5.4.18 or >=5.5.1

Due the changes introduced in the intl extension for fix #62759 now the third argument returns an empty string if is null or 0

Open bug #66219 due the BC break introduced in the previous change.
Skip test if Intl extension is not loaded
Enable Travis Fast finishing

http://about.travis-ci.org/docs/user/build-configuration/#Fast-finishing
Apply workaround just for null value
Merge pull request #5576 from Maks3w/feature/travis-fast-finish

Enable Travis Fast finishing
Merge branch 'hotfix/5576'

Close #5576
Merge pull request #5575 from Maks3w/hotfix/php-62759

Fix graphme_substr for PHP >= 5.4.18 or >=5.5.1
[#5575] Fix skip message

- s/intl/iconv/
Merge branch 'hotfix/5575'

Close #5575
Improvement to #5254

- Do not check on the writer name, only the presence, type, and
  availability of the "db" option value.

  See https://github.com/zendframework/zf2/pull/5254#issuecomment-27776073
Merging PR #5588
Merge branch 'weierophinney-hotfix/5254-improvement'

* weierophinney-hotfix/5254-improvement:
  Improvement to #5254