use https for npmjs.org endpoint

[doiron]

I'm submitting a...

[ ] Regression (a behavior that used to work and stopped working in a new release)
[ ] Bug report  
[ ] Performance issue
[ ] Feature request
[ ] Documentation issue or request 
[X] Other... Please describe: 
- avoid a 302 HTTP to HTTPS redirection

https://github.com/alexa/ask-cli/blob/12c0f97afe9150e66b681aa005160e6d2fcad886/lib/utils/constants.js#L4

Expected Behavior

endpoint should be https

Current Behavior

currently http

CLI Snapshot If applicable, add screenshots to help explain your problem.

Steps to Reproduce (for bugs)

Possible Solution

Your Environment and Context

• ask-cli version: x.x.x
• Operating System and version:
• Node.js version used for development:
• NPM version used for development:

[jsetton]

It looks like #411 was reverted with the 2.29 merge.