Add owner of poolboy in hex.pm

[getong]

Just like proper-testing/proper#176, a new owner of the proper is added in hex.pm.
I think @devinus you should add @Vagabond to be a new owner of the poolboy in the hex.pm, and finally push poolboy 1.5.2 to the hex.pm.

[getong]

@Vagabond
I find out a link, it might be help.
https://hex.pm/policies/dispute#if-you-wish-to-acquire-an-existing-package-name
Would you do the instruction as the page described?

[Vagabond]

I have started this process, we will see where it goes.

[getong]

@Vagabond
I find out that you are the owner of poolboy in the hex.pm, would you publish the new tag to hex.pm?

[Vagabond]

Done!