Fix grammar

It repeats **a method**, not _a methods_.

Author: hkdobrev

index.html

@@ -35,7 +35,7 @@ <h3>
 <h3>
 <a id="what-does" class="anchor" href="#what-does" aria-hidden="true"><span class="octicon octicon-link"></span></a>How does it work?</h3>
 
-<p>It repeats a methods in benchmarking class and tells you the average time it takes to execute the method.</p>
+<p>It repeats a method in benchmarking class and tells you the average time it takes to execute the method.</p>
 
 <p>It also: performs multiple <b>iterations</b>, generates <b>reports</b>, provides <b>statistics</b> (including standard deviation and z-values), enforces <b>stability</b>, supports different <b>time units</b> and output <b>modes</b> and lots more.
 </p>