Readme: Fix typo in alt text of Slack Badge

README.md

 # node-sass
 
-#### Supported Node.js versions 0.10, 0.12, 1, 2, 3, 4, 5, 6 and 7.
+#### Supported Node.js versions 0.10, 0.12, 1, 2, 3, 4, 5, 6, 7 and 8.
 
 <table>
   <tr>
@@ -22,7 +22,7 @@
 [![devDependency Status](https://david-dm.org/sass/node-sass/dev-status.svg?theme=shields.io)](https://david-dm.org/sass/node-sass#info=devDependencies)
 [![Coverage Status](https://coveralls.io/repos/sass/node-sass/badge.svg?branch=master)](https://coveralls.io/r/sass/node-sass?branch=master)
 [![Inline docs](http://inch-ci.org/github/sass/node-sass.svg?branch=master)](http://inch-ci.org/github/sass/node-sass)
-[![Join us in Slakc](https://libsass-slack.herokuapp.com/badge.svg)](https://libsass-slack.herokuapp.com/)
+[![Join us in Slack](https://libsass-slack.herokuapp.com/badge.svg)](https://libsass-slack.herokuapp.com/)
 
 Node-sass is a library that provides binding for Node.js to [LibSass], the C version of the popular stylesheet preprocessor, Sass.