Add PHP 5.5 to Travis config
iconv related functions are deprecated in PHP 5.6
Adds tests cases for String related classes.
Fix some code standard issues in tests.
Fixes code standard issues and correct type of assertion used in a test.
Merge pull request #3 from Achal-Aggarwal/unit-tests

Adds some tests.
Merge pull request #2 from joomla-framework/php56

iconv related functions are deprecated in PHP 5.6
Clean up method internals
Fix tests