Fix for 4 vulnerable dependency paths
Fix for 4 vulnerable dependency paths

generator-htmlemail currently has a 15 vulnerable dependency paths, introducing 7 different types of known vulnerabilities.

This PR fixes 4 vulnerable dependency paths.
* [ReDOS vulnerability](https://snyk.io/vuln/npm:hawk:20160119) in the `hawk` dependency.
* [remote memory exposure ](https://snyk.io/vuln/npm:request:20160119) vulnerability in the `request` dependency.
* [Denial of Service (Event Loop Blocking) vulnerability](https://snyk.io/vuln/npm:qs:20140806-1) in the `qs` dependency.
* [Denial of Service (Memory Exhaustion)](https://snyk.io/vuln/npm:qs:20140806) in the `qs` dependency.

You can see [Snyk test report](https://snyk.io/test/github/jahvi/generator-htmlemail) of this project for details. 

This PR changes `Package.json` to upgrade `request` to the newer 2.74.0 version, and will fix all the vulnerabilities listed above.

You can get alerts and fix PRs for future vulnerabilities for free by [watching this repo with Snyk](https://snyk.io/add).

Note this PR fixes all the vulnerabilities introduced trough `request` dependency, in order to be vulnerability free you will need to upgrade ` yeoman-generator` dependency as well.

Full disclosure: I'm a part of the Snyk team, just looking to spread some security goodness and awareness ;)
jahvi/generator-htmlemail,jahvi/generator-htmlemail