Added take until methods to observables

[pastorsj]

PR Checklist

Please check if your PR fulfills the following requirements:

• Tests for the changes have been added (for bug fixes / features)
• [x Docs have been added / updated (for bug fixes / features)

PR Type

What kind of change does this PR introduce?

[ ] Bugfix
[ ] Feature
[x] Code style update (formatting, local variables)
[x] Refactoring (no functional changes, no api changes)
[ ] Build related changes
[ ] CI related changes
[ ] Documentation content changes
[ ] Other... Please describe:

What is the current behavior?

Issue Number: #60

What is the new behavior?

We now manage subscriptions using Subjects

Does this PR introduce a breaking change?

[ ] Yes
[x] No

If yes, is the package.json file updated accordingly

Other information

[pastorsj]

Approved