Merge branch 'add-droplr-plugin'

Closes #1972.

plugins/droplr/README.md

+# droplr
+
+Use [Droplr](https://droplr.com/) from the comand line to upload files and shorten
+links. It needs to have [Droplr.app](https://droplr.com/apps) installed and logged
+in. MacOS only.
+
+To use it, add `droplr` to the `$plugins` variable in your zshrc file:
+
+```zsh
+plugins=(... droplr)
+```
+
+Author: [Fabio Fernandes](https://github.com/fabiofl)
+
+## Examples
+
+- Upload a file: `droplr ./path/to/file/`
+
+- Shorten a link: `droplr http://example.com`

plugins/droplr/droplr.plugin.zsh

+# Only compatible with MacOS
+[[ "$OSTYPE" == darwin* ]] || return
+
+droplr() {
+    if [[ $# -eq 0 ]]; then
+        echo You need to specify a parameter. >&2
+        return 1
+    fi
+
+    if [[ "$1" =~ ^http[|s]:// ]]; then
+        osascript -e "tell app 'Droplr' to shorten '$1'"
+    else
+        open -ga /Applications/Droplr.app "$1"
+    fi
+}