doc: update CI documentation

- use cloud.drone.io badges for builds on the master branch
- stable/0.x badges will need to be updated when the next stable/0.x release is published

README.md

@@ -13,7 +13,7 @@ _It is designed to be personal (single-user), fast and handy._
 [![](https://img.shields.io/travis/shaarli/Shaarli/latest.svg?label=latest)](https://travis-ci.org/shaarli/Shaarli)
 •
 [![](https://img.shields.io/badge/master-v0.12.x-blue.svg)](https://github.com/shaarli/Shaarli)
-[![](https://img.shields.io/travis/shaarli/Shaarli.svg?label=master)](https://travis-ci.org/shaarli/Shaarli)
+[![](https://cloud.drone.io/api/badges/shaarli/Shaarli/status.svg?ref=refs/heads/master)](https://cloud.drone.io/shaarli/Shaarli)
 
 [![Join the chat at https://gitter.im/shaarli/Shaarli](https://badges.gitter.im/Join%20Chat.svg)](https://gitter.im/shaarli/Shaarli)
 [![Bountysource](https://www.bountysource.com/badge/team?team_id=19583&style=bounties_received)](https://www.bountysource.com/teams/shaarli/issues)

doc/md/dev/Development.md

@@ -143,17 +143,17 @@ A [`Makefile`](https://github.com/shaarli/Shaarli/blob/master/Makefile) is avail
 
 ### Continuous Integration
 
-[Travis CI](http://docs.travis-ci.com/) is a Continuous Integration build server, that runs a build:
+[Drone CI](https://cloud.drone.io/shaarli/Shaarli) is a Continuous Integration build server, that runs a build:
 
-- each time a commit is merged to the mainline (`master` branch)
+- each time a commit is pushed to any branch
 - each time a Pull Request is submitted or updated
 
-After all jobs have finished, Travis returns the results to GitHub:
+After all jobs have finished, Drone returns the results to GitHub:
 
-- a status icon represents the result for the `master` branch: [![](https://api.travis-ci.org/shaarli/Shaarli.svg)](https://travis-ci.org/shaarli/Shaarli)
-- Pull Requests are updated with the Travis build result.
+- a status icon represents the result for the `master` branch: [![Build Status](https://cloud.drone.io/api/badges/shaarli/Shaarli/status.svg?ref=refs/heads/master)](https://cloud.drone.io/shaarli/Shaarli)
+- Pull Requests are updated with the Drone build result.
 
-See [`.travis.yml`](https://github.com/shaarli/Shaarli/blob/master/.travis.yml).
+See [`.drone.yml`](https://github.com/shaarli/Shaarli/blob/master/.drone.yml).
 
 
 ### Documentation