Updates module reference Hashie::HashExtensions to Hashie::Extensions.

Signed-off-by: Jonmichael Chambers <jon@tyrbo.net>
Changes Gemfile to use gemspec file.
Specifies a version ~> 3.0.0 for hashie gem.

Signed-off-by: Jonmichael Chambers <jon@tyrbo.net>
Merge pull request #5 from tyrbo/hashie_fix

Updates module reference Hashie::HashExtensions to Hashie::Extensions.