HistoriesClient#downloadDataset mangles HTML file contents

Downloading an HTML Galaxy output file (in my case, a QUAST HTML output report) with [`HistoriesClient#downloadDataset`](https://github.com/galaxyproject/blend4j/blob/master/src/main/java/com/github/jmchilton/blend4j/galaxy/HistoriesClientImpl.java#L112) results in a binary file with mangled contents, while downloading from `galaxyUrl + downloadUrl` of the `DataSet` object corresponding to the HTML file in Galaxy conserves the file format (tested with Clojure's [`slurp`](https://clojuredocs.org/clojure.core/slurp) method).

Start in src/main/java/com/github/jmchilton/blend4j/galaxy/HistoriesClientImpl.java at HistoriesClient#downloadDataset, then compare its handling with downloading the DataSet object's galaxyUrl + downloadUrl. Confirm the behavior with an HTML Galaxy output such as a QUAST report; done means the downloaded contents preserve the original HTML format.

Written by the indexing model from the issue text.