Install script can abort on mkdir

[solarizedalias]

Describe the bug

Currently, install.sh (invoked by doge#install()) can fail if $ROOT_DIR/bin already exists (e.g. when users try to update the plugin). This happens because mkdir ./bin returns non-zero when the directory exists and set -e causes the entire script to abort, therefore results in empty bin directory (the binary, if exists, is removed every time the script runs).

Settings

To Reproduce
Run call doge#install() or scripts/install.sh more than one time.

Expected behavior
The script does not abort and the binary vim-doge is installed in bin properly.

[kkoomen]

I don't know which system you're running, but I don't have this problem on OSX, but I did add a check now. Shouldn't have this issue again in v3.3.1. Let me know if it's fixed for you or not.

[solarizedalias]

Thank you, looks like it's solved.
Updated the plugin and confirmed doge#install() or running install.sh downloads the latest binary each time they run.

It's strange because I also use macOS (mojave), I tried in two versions of mkdir, /bin/mkdir and coreutils mkdir installed by homebrew by modifying PATH, which in this case behaved the same way. mkdir: cannot create directory ‘./bin’: File exists