ci: configure cache for yarn and node_modules

[Kocal]

Changements apportés dans cette pull request :

• Configuration du cache Travis pour yarn et le dossier node_modules

[codecov]

Codecov Report

Merging #200 into develop will not change coverage.
The diff coverage is n/a.

@@           Coverage Diff            @@
##           develop     #200   +/-   ##
========================================
  Coverage    88.83%   88.83%           
========================================
  Files           15       15           
  Lines          215      215           
  Branches        32       32           
========================================
  Hits           191      191           
  Misses          22       22           
  Partials         2        2

---

Continue to review full report at Codecov.

Legend - Click here to learn more
Δ = absolute <relative> (impact), ø = not affected, ? = missing data
Powered by Codecov. Last update 0f1a214...b3dbba8. Read the comment docs.