Support for Angular 6, rxjs 6

[filipjnc]

Will fix #39 and #43.

[cogni-prasant]

i have purchased material dashboard angular.. but i am facing problm with installing..
C:\ang\dashboard>npm install
npm WARN deprecated tslint@6.0.0: TSLint has been deprecated in favor of ESLint. Please see palantir/tslint#4534 for more information.
npm WARN deprecated @angular/http@7.2.16: Package no longer supported. Use @angular/common instead, see https://angular.io/guide/deprecations#angularhttp
npm WARN deprecated popper.js@1.16.1: You can find the new Popper v2 at @popperjs/core, this package is dedicated to the legacy v1
npm WARN deprecated eivindfjeldstad-dot@0.0.1: Use @eivifj/dot instead
npm WARN deprecated request@2.88.2: request has been deprecated, see request/request#3142
npm ERR! code Z_BUF_ERROR
npm ERR! errno -5
npm ERR! zlib: unexpected end of file

npm ERR! A complete log of this run can be found in:
npm ERR! C:\Users\dell\AppData\Roaming\npm-cache_logs\2020-02-29T20_00_11_793Z-debug.log