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ARROW-672: [Format] Add MetadataVersion::V3 for Arrow 0.3

As a matter of diligence, we increment the metadata version for Arrow 0.3 since we've changed the metadata format is various ways.

Author: Wes McKinney <wes.mckinney@twosigma.com>

Closes #488 from wesm/ARROW-672 and squashes the following commits:

f39733e [Wes McKinney] Add C++ unit test for read/write MetadataVersion. Change MetadataVersion to C++11 enum class
bb09ba2 [Wes McKinney] Add MetadataVersion::V3 for Arrow 0.3