fix(addStyles): correctly check singleton behavior when {Boolean} (options.singleton)

[alexander-akait]

What kind of change does this PR introduce?

bugfix

Did you add tests for your changes?

yes

If relevant, did you update the README?

yes, we don't have singleton option in table options, i don't know how it is happens

Summary

When singleton: true - i want to use one style tag.
When singleton: false - i want to use multiple style tags.
When singleton not specify (i.e. undefined) - i want the loader himself decide to use single or multiple style tags.

Issue: #283

Does this PR introduce a breaking change?

No

Other information

[alexander-akait]

Btw be great to ensure isOldIE called or not using sinon, i try to found how to test this.
Seems this can not be done with sinon, we can add tests when migrate to jest.