tec: Fix Travis build
tec: Fix Travis build

For no reason, NPM isn't capable to install dependencies.
So for no reason, I add a `npm cache clean` command before install.
And still for no reason, it will solve the issue.

Thank you NPM.

marienfressinaud/project-zero,marienfressinaud/project-zero,marienfressinaud/lessy,marienfressinaud/project-zero,marienfressinaud/lessy,marienfressinaud/lessy