make resname optional, use id as identifier
add optional resource_name to README
fix wrong method-name to_xliff in README
introducing CHANGELOG.md
add date to changelog
add specs for Xliffle:String and Xliffle:File
bump version to 0.2.0
add specs to changelog
update Gemfile.lock
add spec for adding a note
remove id from file initializer
Merge pull request #4 from sr189/feature/use_string_ids

Xliffle 0.2.0
Merge branch 'release/xliffle-02.0' into develop
Merge branch 'develop' of github.com:sr189/xliffle into develop
Merge branch 'develop'