feat(deployment-logs): display the last deployment logs if none is provided

[EtienneM]

╰─$ go build -o scalingo-cli ./scalingo && ./scalingo-cli -a my-app deployment-logs                                     
       -----> Selected the most recent deployment (ca874847-654d-455e-a7d5-dcab193413f1)                                                                                                                           
 <-- Start deployment of my-app -->                                                                                                                                                                                
       Fetching source code                                                                                                                                                                                        
...

Fix https://github.com/Scalingo/one-stop-shop/issues/62

• Add a changelog entry in the section "To Be Released" of CHANGELOG.md