Fixes install --github so it append README.md

- Before it replaced the README.md file with new content, now its
append content in a more proper manner. If no README.md exists its
still created.
- .localeapp was sometimes injected without space on the previous
.gitignore key, now it ensure newline.
Extract synchronisation data into SyncFile and SyncData classes

- These value objects allow us to read synchronisation data from yaml files that have both strings and symbols as keys.

- Sync files now use strings as keys when serialising to yaml.

Fixes #149
Fix test for yaml output format in ruby 1.9.3
Merge pull request #154 from Locale/issue_149

Extract synchronisation data into SyncFile and SyncData classes
Merge pull request #152 from futhr/feature/append-readme

Fixes install --github so it append README.md