index.html: change to "Install" instead of "Get Started"

"Get Started" sounds vague and cumbersome (analogous to "Call for
a quote!" instead of just saying what the price is).

Author: justinmk

index.html

@@ -9,7 +9,7 @@
 
 <section class="masthead">
   <h1 class="lead">hyperextensible Vim-based text editor</h1>
-  <p><a href="https://github.com/neovim/neovim/wiki/Installing-Neovim" class="btn">Get Started</a></p>
+  <p><a href="https://github.com/neovim/neovim/wiki/Installing-Neovim" class="btn">Install Now</a></p>
 </section>
 
 <section class="front-section">