Encode URLs

[KevCaz]

I am currently not able to test updated_since because of a mismatch between the request and what's recorded

request:

https://api.speciesplus.net/api/v1/taxon_concepts.json?updated_since=2018-01-01T00%3A00%3A00&page=1&per_page=500

and the cassette:

https://api.speciesplus.net/api/v1/taxon_concepts.json?updated_since=2018-01-01T00:00:00&page=1&per_page=500

One possible way around is to use utils::encodeURL()

[KevCaz]

Depending on this I may or may not use utils::encode() ropensci/vcr#240

[KevCaz]

There are several good options, can't say they're all as good, but I don't see any major drawback for any of those:

1. using modify_url() from httr
2. using curl::curl_escape() which is used at some point by httr::modify_url()
3. using utils::encode() which I do.

None of them will actually add the dependencies list because the 3 packages area already direct or indirect depencies.

[KevCaz]

This has been fixed in vcr see ropensci/vcr#247.