feat: URL encode dataset

[MikeGoldsmith]

Which problem is this PR solving?

When sending data, the dataset name forms part of the URL path and should be URL encoded so restricted characters are preserved. This is particularly important if the dataset name included a forward slash / which results in an invalid URL path and the Honeycomb API rejecting the request.

Short description of the changes

• URL encode the dataset before sending data
• Add tests to verify dataset is encoded correctly for use in the request path