Update to commit 13aff14 from git@github.com:gedex/wp-slack.git

Includes the following commit(s):

commit 13aff141ea6be987e8da0ae07ce871f8c9c15069
Author: Akeda Bagus <akeda@x-team.com>

    Bump version 0.5.0.

M	includes/plugin.php
M	readme.md
M	readme.txt
M	slack.php

commit 4950e3fdb127ed40c354b915e82fbbc2822385b1
Author: Akeda Bagus <akeda@x-team.com>

    Removed unused doc that confuse new contributors.

D	bin/contributing.md
D	bin/readme.md

commit 2bd4e293ad898ec93357aad19b0336dcf083088b
Author: Akeda Bagus <akeda@x-team.com>

    Added reedyn to contributors list.

M	readme.md
M	readme.txt

commit 50c0ba1655f5bc5fb6adbb9b5f1d6b14579e5ee7
Merge: 7438f31 c4c1763
Author: Akeda Bagus <akeda@x-team.com>

    Merge branch 'KarsOrdet-develop'

commit c4c1763dd24467d7da57eaf07057544e731bd788
Author: Akeda Bagus <akeda@x-team.com>

    More verbose description of icon_emoji field.

M	views/post-meta-box.php

commit 62dd3404808d214d41b3b273af2ecd355367c47c
Author: Akeda Bagus <akeda@x-team.com>

    Fixed indentation.

M	views/post-meta-box.php

commit 217a477bd1bc4e40d16981a0b7e014f281eacc4b
Author: Gustav Lindqvist <gustav@glindqvist.se>

    Added support for custom emoji icon

M	includes/event-payload.php
M	includes/post-meta-box.php
M	js/admin.js
M	views/post-meta-box.php


git-svn-id: https://plugins.svn.wordpress.org/slack/trunk@945146 b8457f37-d9ea-0310-8a92-e5e31aec5664