PARQUET-418: Refactored parquet_reader utility for printing file contents.
PARQUET-418: Refactored parquet_reader utility for printing file contents.

This pull request contains the following changes:
* Modified parquet_reader utility: refactored, fixed memory leaks, merged compute_stats utility to get rid of code duplication.
* Added a flag --only-stats to parquet_reader to print only file statistics.
* Modified InMemoryInputStream to own its buffer.

All the code repetition still remaining in parquet_reader clearly highlights the need for specialized ColumnReader classes. I will create a new JIRA for this improvement.

Author: Aliaksei Sandryhaila <aliaksei.sandryhaila@hp.com>

Closes #18 from asandryh/PARQUET-418 and squashes the following commits:

a378a1e [Aliaksei Sandryhaila] Changed the buffer in ScopedInMemoryInputStream to std::vector.
7f6f533 [Aliaksei Sandryhaila] [PARQUET-418]: Added/modified a utility for printing a file contents.

Change-Id: I68ab468567935551dbf1ab5304d4959cdebe0ad4

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