v0.13.4

Clustering v0.13.4

Diff since v0.13.3

Changelog:

• hclust(): handle duplicate distances better (#176 #177) (@alyst)
• kmeans corner cases for k=1 and k=n (#183, #185) (@birm)
• rename KmedoidsResults.acosts to costs (#98, #186) (@birm)
• Correct & expand k-medoids implementation note (#178, #187) (@alyst)
• Install TagBot as a GitHub Action (#184) (@JuliaTagBot)
• Fix Travis CI (#189) (@alyst)