Add IncreasingPriceCrowdsale to documentation

contracts/crowdsale/README.adoc

@@ -6,6 +6,10 @@ NOTE: This page is incomplete. We're working to improve it for the next release.
 
 {{Crowdsale}}
 
+== Price
+
+{{IncreasingPriceCrowdsale}}
+
 == Emission
 
 {{AllowanceCrowdsale}}