[TypeScript][Aurelia] Enhancements and bug fixes

Description

Here is list of enhancements and bug fixes for typescript-aurelia:

• Resolve errors when running npm install (details see below)
• Create shell scripts, batch files to generate TS Aurelia Petstore samples
• Setup CI (travis, shippable, etc) to cover the TS Aurelia Petstore samples.
• Add support for validation rules defined in the spec (e.g. validation for parameters in Ruby API layer)

Swagger-codegen version

Latest master

Command line used for generation

./bin/typescript-aurelia-petstore.sh or .\bin\windows\typescript-aurelia-petstore.bat

Related issues/PRs

https://github.com/swagger-api/swagger-codegen/pull/5991

Suggest a fix/enhancement

If anyone wants to work on the enhancements or bug fixes, please reply to let us know.

cc @ksm2