Update dependencies to fix security vulnerabilities reported by Snyk

[Holubinka]

Hi,

While using grunt@1.6.1, we ran a snyk test and found security vulnerabilities.

✗ Medium severity vulnerability found in inflight
  Description: Missing Release of Resource after Effective Lifetime
  Info: https://security.snyk.io/vuln/SNYK-JS-INFLIGHT-6095116
  Introduced through: glob@7.1.7
  From: glob@7.1.7 > inflight@1.0.6

Thanks for developing grunt!