Making Hash#pselect work the same as Hash#select

[aaronklor]

When using pselect on hashes, the return is an array of arrays

[['key1', 'value1'], ['key2', 'value2'], ...]

This differs from Hash's implementation that returns a new hash.

{'key1' => 'value1', 'key2' => 'value2', ...}

This PR should resolve this disparity.

Hash#select doc for reference
http://www.ruby-doc.org/core-2.1.0/Hash.html#method-i-select