HistoriesClient#downloadDataset mangles HTML file contents

[peterk87]

Downloading an HTML Galaxy output file (in my case, a QUAST HTML output report) with HistoriesClient#downloadDataset 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 method).