Docs: Run "brew update" before "brew install hugo"

Remind user to always run "brew update" first in order to avoid
repeated bug reports from users who didn't do that.

See #824, #1067, #1537, #1633 and #1749

docs/content/overview/installing.md

@@ -35,7 +35,7 @@ Ideally, you should install it somewhere in your `PATH` for easy use.
 `/usr/local/bin` is the most probable location.
 
 On OS X, if you have [Homebrew](http://brew.sh/), installation is even
-easier: just run `brew install hugo`.
+easier: just run `brew update && brew install hugo`.
 
 For a more detailed explanation follow the corresponding installation guides:
 

docs/content/tutorials/installing-on-mac.md

@@ -59,10 +59,16 @@ When I did this, I had some problems with directory permissions. Searches on Goo
 
 ### Step 2: Run the `brew` command to install `hugo`
 
-Replace `brew install hugo` with `brew install hugo --HEAD` if you
-want the absolute latest version—there might be bugs!
+First, update the formulae and Homebrew itself by running:
 
+```bash
+$ brew update
 ```
+
+Then, install Hugo using Homebrew by running:
+
+
+```bash
 $ brew install hugo
 ==> Downloading https://homebrew.bintray.com/bottles/hugo-0.13_1.yosemite.bottle.tar.gz
 ######################################################################## 100.0%
@@ -70,9 +76,13 @@ $ brew install hugo
 🍺  /usr/local/Cellar/hugo/0.13_1: 4 files,  14M
 ```
 
+(Note: Replace `brew install hugo` with `brew install hugo --HEAD`
+if you want the absolute latest version in development,
+but beware—there might be bugs!)
+
 `Brew` should have updated your path to include Hugo. Confirm by opening a new terminal window and running a few commands:
 
-```
+```bash
 $ # show the location of the hugo executable
 $ which hugo
 /usr/local/bin/hugo

docs/layouts/index.html

@@ -223,7 +223,7 @@
                 <a href="/overview/quickstart/" style="color:white;font-weight:300;">Quickstart Guide</a>
                 <p>&nbsp;</p>
                 <h4>Using Homebrew?</h4>
-                <pre><code>brew install hugo</code></pre>
+                <pre><code>brew update &amp;&amp; brew install hugo</code></pre>
               </div>
             </div>
           </div>

docs/static/css/HPstyles.css

@@ -205,7 +205,6 @@ i.callout-icon:hover {
     color: #545454;
 }
 #action code {
-    font-family: Lato, monospace;
     font-size: 14pt;
 }