upgrade node version to 10.15

[patitonar]

Updated .nvmrc and dockerfile to use version 10.

Also npm vulnerabilities were fixed, now npm audit report shows only 31 vulnerabilities that are related to dependencies of react-scripts. Upgrading react-scripts introduce some breaking changes to react-app-rewired and react-app-rewire-mobx which will require some configuration updates (and possibly a new dependency). Given that react-scripts is used to avoid configuration for development and build process I think it's ok for now to have these vulnerabilities.

found 31 vulnerabilities (29 low, 2 high) in 105330 scanned packages
  31 vulnerabilities require semver-major dependency updates.

Closes #177

[netlify[bot]]

Deploy preview for kind-kilby-95344f processing.

Building with commit 7bd57724c010e000fa340560e42a7d8b973296b2

https://app.netlify.com/sites/kind-kilby-95344f/deploys/5c94ef059e64510008672c89

[coveralls]

Pull Request Test Coverage Report for Build 383

• 0 of 0 changed or added relevant lines in 0 files are covered.
• 13 unchanged lines in 1 file lost coverage.
• Overall coverage increased (+1.7%) to 4.897%

---

Files with Coverage Reduction	New Missed Lines	%
src/stores/TxStore.js	13	13.39%
<!--	Total:	13		-->

Totals
Change from base Build 341:	1.7%
Covered Lines:	71
Relevant Lines:	1081

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💛 - Coveralls

[patitonar]

Netlify deploy failed because submodule repo didn't support Node 10. After updating to latest commit on 119-Epic-rewards-for-bridge-validators build now is working