Merge pull request #74 from satoshi-takano/bump_up_version

Bump up version to 1.6.0

Bump up version to 1.5.0

Bump up version to 1.4.1

Fix

Bump up version

Update IPHONEOS_DEPLOYMENT_TARGET

Merge pull request #47 from satoshi-takano/add_public_initializer

Add public initializer to OpenGraph class

Bump up version

Merge branch 'master' of github.com:satoshi-takano/OpenGraph

Merge pull request #40 from satoshi-takano/update_regex

Accept some edge case