[Format] Bump metadata version for 0.3 release

[asfimport]

Reporter: Wes McKinney / @wesm
Assignee: Wes McKinney / @wesm

Related issues:

• Arrow 0.3 release (blocks)

_{Note: This issue was originally created as ARROW-672. Please see the migration documentation for further details.}

[asfimport]

Wes McKinney / @wesm:
PR: #488

[asfimport]

Wes McKinney / @wesm:
Issue resolved by pull request 488
#488