Fix travis error

[IljaN]

> contacts@1.5.0 prebuild /home/travis/build/owncloud/contacts
> npm install && npm update && node_modules/bower/bin/bower install && node_modules/bower/bin/bower update
npm ERR! Buffer.alloc is not a function
npm ERR! A complete log of this run can be found in:
npm ERR!     /home/travis/.npm/_logs/2017-09-05T12_06_48_069Z-debug.log
npm ERR! code ELIFECYCLE
npm ERR! errno 1
npm ERR! contacts@1.5.0 prebuild: `npm install && npm update && node_modules/bower/bin/bower install && node_modules/bower/bin/bower update`
npm ERR! Exit status 1
npm ERR! 
npm ERR! Failed at the contacts@1.5.0 prebuild script.
npm ERR! This is probably not a problem with npm. There is likely additional logging output above.
npm WARN Local package.json exists, but node_modules missing, did you mean to install?
npm ERR! A complete log of this run can be found in:
npm ERR!     /home/travis/.npm/_logs/2017-09-05T12_06_48_086Z-debug.log
make[1]: *** [npm] Error 1
make[1]: Leaving directory `/home/travis/build/owncloud/contacts'
make: *** [build] Error 2

[codecov-io]

Codecov Report

Merging #617 into master will not change coverage.
The diff coverage is n/a.

@@           Coverage Diff           @@
##           master     #617   +/-   ##
=======================================
  Coverage   18.72%   18.72%           
=======================================
  Files          51       51           
  Lines        1036     1036           
=======================================
  Hits          194      194           
  Misses        842      842

---

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