Don't assume logical numeric config values are strings

[JoeGermuska]

In updating the main website example with recent code changes, this line throws an error when the value of config.slider.start_at_card is a number.

The workaround is to make it a string (so that it has a replace function), but that isn't something users of the library should need to know. We should change it to not get hung up on this.

storyline/src/js/data.js

Line 272 in fa7c066

formattedHeaders[header] = "gsx$" + configSubset[key][header].replace(/\s/g, '').toLowerCase()

[JoeGermuska]

@shortdiv can you review this and verify that it's fixed or fix?

[shortdiv]

Will do! 👍