`-t` flag fails to download posts when tags contain colons#49

I tried to use the `-t` flag to try to download only posts with specific tags, but it doesn't seem to work for any tags that have colons in them. For example, I tried to download `https://beyondhope.tumblr.com/tagged/tv: north and south` using ``` tumblr-backup -S -R -r --no-post-clobber --save-notes --media-list --save-video --save-audio --threads 1 -i -t "tv: north and south" beyondhope ``` but no posts get downloaded. I also tried the following variations (with the `-t` option), none of which worked either: ``` "tv%3A north and south" "tv%3A%20north%20and%20south" tv%3A%20north%20and%20south "tv\\:: north and south" "tv\: north and south" "tv\\: north and south" "tv\:: north and south" ``` Another example: if I run ``` tumblr-backup -S -R -r --no-post-clobber --save-notes --media-list --save-video --save-audio --threads 1 -i -t "farscape","tv: farscape","john x aeryn","ben browder","claudia black","john crichton","aeryn sun" beyondhope ``` It successfully saves posts tagged with any of "farscape", "john x aeryn", "ben browder", "claudia black", "john crichton", or "aeryn sun". However, no posts tagged "tv: farscape" download unless they included one of the above tags also.