Export 'configure' section of prereqs when meta-spec version 2.

The 'configure' section of prereqs is not exported when meta-spec is version 2, but exported at the version 1.4.

'configure' section should be exported at any of the version of meta-spec.
Fix pod for BUILD_REQUIRES.

'BUILD_REQUIRES' is set to { "ExtUtils::MakeMaker" => 0 } at default, but this is not documented.
Merge pull request #77 from magnolia-k/master

'configure' section of prereqs of CPAN meta file is not exported when meta-spec version 2.