Make URLs in document consistent and secure

[aeroastro]

What was the end-user problem that led to this PR?

There are 3 documentation problems

• End-users experience 301 redirect when visiting http://www.bundler.io and http://bundler.io
• End-users might accidentally send email addresses via http version of https://slack.bundler.io, which is not redirected automatically.
• Partially fixing this is O.K., but consistent URLs throughout the documentation are easy to use.

What was your diagnosis of the problem?

I have manually visited the Slack invitation URL on https://bundler.io/ and noticed the problem.
Following are the simple curl command to explain this problem.

$ curl -I  http://slack.bundler.io
HTTP/1.1 200 OK
Server: Cowboy
Connection: keep-alive
X-Powered-By: Express
Content-Type: text/html; charset=utf-8
Content-Length: 3726
Etag: W/"QPm3qygnJrqeFm+KK+VifA=="
Date: Mon, 28 Jan 2019 07:32:02 GMT
Via: 1.1 vegur

$ curl -I http://www.bundler.io
HTTP/1.1 301 Moved Permanently
Content-Type: text/html; charset=utf-8
Location: https://bundler.io
X-Redirector-Version: 84a0a5c
Date: Mon, 28 Jan 2019 07:32:28 GMT

$ curl -I http://bundler.io
HTTP/1.1 301 Moved Permanently
Server: GitHub.com
Content-Type: text/html
Location: https://bundler.io/
X-GitHub-Request-Id: FF7E:37F3:4DD47F:595032:5C4EB012
Content-Length: 178
Accept-Ranges: bytes
Date: Mon, 28 Jan 2019 07:32:35 GMT
Via: 1.1 varnish
Age: 0
Connection: keep-alive
X-Served-By: cache-nrt6127-NRT
X-Cache: MISS
X-Cache-Hits: 0
X-Timer: S1548660755.461639,VS0,VE91
Vary: Accept-Encoding
X-Fastly-Request-ID: 8c832766ee3154dc26abd3e1adcd1258a243e4ce

What is your fix for the problem, implemented in this PR?

My fix is to replace old URLs with new URLs.

• Replace Slack invitation URLs with safe https ones
• Replace http://www.bundler.io with https://bundler.io
• Replace http://bundler.io with https://bundler.io

Why did you choose this fix out of the possible options?

Because rewriting URLs on document is easy and simple.
Optionally, if someone could implement 301 redirect on Slack invitation URL, it would further help the issue.

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[greysteil]

❤️

[greysteil]

@bundlerbot r+

[ghost]

Build succeeded

• continuous-integration/travis-ci/push

[aeroastro]

Thank you ❤️