Update Inflector.php

Modified singularizer inside inflector to accurately inflect most words ending in -aves. Removed irregular cases solved by this fix.
Update InflectorTest.php

Added test cases for changes to inflector which affected words ending -aves. Author acknowledges the homonym conflict with 'leaves' and 'leaves', but preferences the word whose singular avoids an exception to the inflection rule.
Merge pull request #3069 from wbkostan/master

Modifications to singulizer rules for Inflector.php. Supported with test cases