Enforce git-flow, PR and squash commit about curv

[gbenattar]

Merging to master is possible only if

• A PR received approval
• Status check with Travis passed
• Performed by an administrator

In addition, only squash commit from PR is enabled.

[gbenattar]

When working on a change:

• A github issue must be created
• The name of the branch must be feature/[issue number], E.g. feature/66
• The description of the PR has to be explicit. E.g.

Title: Introducing new curve ABCD

Motivation: ABCD is used in blockchain Z
Test: Unit test added and integration test against Z done etc...
Related Issue: 66

[gbenattar]

I am closing this task.
Feel free to re-open if you have any questions.