Classes fail to load when not packaged with Parquet.

Parquet cannot dynamically load classes from another package. This has already been noticed and addressed here: https://github.com/Parquet/parquet-mr/pull/289

However, the fix didn't address all occurrences of Class.forName. parquet-cascading jobs fail trying to load cascading.scheme.Scheme, even though it is present on the classpath.

This bug shows up in cloudera distributions of parquet since they provide parquet jars on the hadoop classpath.

**Reporter**: [Alex Robbins](https://issues.apache.org/jira/secure/ViewProfile.jspa?name=alexrobbins)

_{**Note**: *This issue was originally created as [PARQUET-261](https://issues.apache.org/jira/browse/PARQUET-261). Please see the [migration documentation](https://issues.apache.org/jira/browse/PARQUET-2502) for further details.*}

まず pull request 289 を確認し、cascading.scheme.Scheme のロードに関連する残りの Class.forName の出現箇所を特定します。Hadoop のクラスパスに Parquet の JAR を配置して parquet-cascading の失敗を再現し、その後、別のパッケージのクラスがクラスパス上に存在する場合に正常にロードされることを確認します。

索引モデルが issue の本文から書いたものです。