Create an API endpoint to download data from NCBI - through Download tool of Candis.

[rupav]

This will be used to download data from NCBI into Candis.

Checklist: to implement

• [x] Add API endpoint to call Entrez module.
• [x] Add GEO module
• [x] Implement Esearch
• [x] Implement Esummary
• [x] Implement the logic as described in https://www.ncbi.nlm.nih.gov/geo/info/geo_paccess.html#ExampleIII
• [x] Use socket.io for download progress.
• [ ] Add test cases
• [x] Remove time.sleep()
• [x] Setup logging instead of print statements. - refer #137
• [x] Start redis server from ~Procfile~ (now using honho Manager class) - use different port if initialized. - refer #99
• [ ] ftplib is used for downloading- show progress bar (It shows up with 'wget')
• [x] Integrate with front-end. - refer issue #110 TODO: Improvements needed as mentioned in the related PRs to #110
• [ ] Add JS test cases for the same.
• [ ] Instead of using requests.Timeout error, use custom error class.