Mention yarn in docs and update lockfile (#536)

.github/ISSUE_TEMPLATE.md

@@ -5,9 +5,9 @@ Before you continue; please make sure you've searched our existing issues to avo
 
 macOS Version:        The output of `sw_vers`, remember that we currently only support macOS 10.12 or later 
 Kap Version:          Find this in the about section of Kap, or by right clicking on the Kap icon and pressing "Get Info"
-Step to reproduce :   If applicable provide steps to reproduce the issue you're having
+Step to reproduce:    If applicable provide steps to reproduce the issue you're having
 Current behaviour:    A description of how Kap is currently behaving
-Expected behaviour :  How you expected Kap to behave
+Expected behaviour:   How you expected Kap to behave
 Workaround:           A workaround the issue if you've found on (this will help others experiencing the same issue!)
 -->
 

contributing.md

@@ -1,13 +1,13 @@
 # Contributing
 
 1. [Fork](https://help.github.com/articles/fork-a-repo/) this repository to your own GitHub account and then [clone](https://help.github.com/articles/cloning-a-repository/) it to your local device
-2. Install the dependencies: `npm install`
-3. Build the code, start the app, and watch for changes: `npm start`
+2. Install the dependencies: `yarn`
+3. Build the code, start the app, and watch for changes: `yarn start`
 
 To make sure that your code works in the finished app, you can generate the binary:
 
 ```
-$ npm run pack
+$ yarn pack
 ```
 
 After that, you'll see the binary in the `dist` folder 😀

maintaining.md

@@ -3,7 +3,7 @@
 
 ## Developing Kap
 
-Run `npm run dev` in one terminal tab to start watch mode, and in another tab, run `npm start` to launch Kap.
+Run `yarn dev` in one terminal tab to start watch mode, and in another tab, run `yarn start` to launch Kap.
 
 We strongly recommend installing an [XO editor plugin](https://github.com/sindresorhus/xo#editor-plugins) for JavaScript linting and a [Stylelint editor plugin](https://github.com/stylelint/stylelint/blob/master/docs/user-guide/complementary-tools.md#editor-plugins) for CSS linting. Both of these support auto-fix on save.