Get rid of the featured tab. Fixes #503.

This adds a sort of 'welcome' message to the dashboard when you first
log in. I don't know if it's hokey.
anagram_test.rb excludes anagram subsets

Someone sorted letters and then incorrectly did a prefix check instead of a full comparison:

http://exercism.io/submissions/520ea215d908bd42b70005d0
Merge pull request #533 from kytrinyx/ditch-featured

Get rid of the featured tab. Fixes #503.
Trying to nudge towards opening with positive feedback
Add example of how to create a basic node module

It's not at all obvious how to get started exporting an object so it can be loaded by node, and the node documentation is confusing.
Merge pull request #538 from markijbema/positive-feedback

Trying to nudge towards opening with positive feedback
Merge pull request #540 from jvns/patch-1

Add example of how to create a basic node module (#536)
ruby/anagram prefix test checks both ways.

Realized that [the submission that inspired this][1] actually checked for
the candidate as a prefix of the subject, not the other way around.

[1]: http://exercism.io/submissions/520ea215d908bd42b70005d0
Merge pull request #537 from henrik/patch-2

anagram_test.rb excludes anagram subsets
Anagram subset test for other languages than Ruby.
Don't point to where people can find links

Give them something to click on.
Merge pull request #548 from markijbema/patch-2

Don't point to where people can find links
Merge pull request #549 from henrik/patch-3

Test parity: Anagram: subset test
Tweak welcome message
Improve notifications

Use different wording depending on whether this is part of a discussion,
a new submission, or an exercise has been marked as completed.

There is still room for improvement:

Notifications to the submitter about discussion should look different
from notifications to other participants.
Improve notifications

Distinguish between notifications to the submitter and notifications to
participants about new comments/nitpicks.
Fix silly js mistakes
Highlight submitters own comments. Fixes #544
Improve messaging to submitter in discussion. Fixes #543.
Simplify api for Submission#muted_by?