Rename play_pattern_timed durations to beats

This is so I don't forget they're beats, not seconds.

data/post/sonic_pi_example.rb

@@ -23,15 +23,15 @@
     As2  As2  As2  As2
   ]
 
-  times = %w[
+  beats = %w[
     2.0  1.0  1.0
     2.0  1.0  1.0
     2.0  1.0  1.0
     1.5  1.0  0.5  1.0
   ].map(&:to_f)
 
   with_fx :reverb do
-    play_pattern_timed notes, times
+    play_pattern_timed notes, beats
   end
 end
 
@@ -45,14 +45,14 @@
     Eb4   Eb4   F4    Fs4   Eb4
   ]
 
-  times = %w[
+  beats = %w[
     2.00  0.50  0.25  0.25  0.25  0.75  2.00
     0.50  0.25  0.25  0.25  0.75  1.50
     1.00  1.00  1.00  1.00
     0.50  0.50  0.50  0.50  0.50
   ].map(&:to_f)
 
   with_fx :reverb do
-    play_pattern_timed notes, times
+    play_pattern_timed notes, beats
   end
 end