[API] [TEST] Fixed incorrect version comparison for "skip" in YAML tests

Previously, the "min" and "max" versions have been compared to actual
version naively, by string comparison, leading to broken builds such as:

--> http://build.elasticsearch.com/job/es-ruby_core/ES_V=0.90_nightly,RUBY_V=1.9.3-p448,TEST_TYPE=integration,label=not-es/lastCompletedBuild/testReport/

With this patch, all version strings are "normalized" to the
`000-000-000` format, thus supporting comparisons such as:

    "000.090.003" < "000.090.010"

The normalization code is directly based on the Perl client's implementation:

--> https://github.com/elasticsearch/elasticsearch-perl/blob/c650f52ed63ca823f8d77fa1251c20a90cf8b02b/t/lib/Elasticsearch/Client/Test.pm#L305