Add Release endpoint
Use latest Retrofit
Allow AppendToResponse on movie summary method
Allow appending on Similar Movies too
Revert "Use latest Retrofit"

This reverts commit a86e4733f4758223fdf772561e3b6787d6000cdf.
Rename `ReleaseResult` to `Releases´.

- Naming more in line with other entities.
Merge branch 'chrisbanes-dev' into dev