Publish docs for rrect, picture, blendmode

Complete basic docs for SkRRect, SkPicture, SkBlendMode.
Add a new rule that checks the main description tense.
Check for spelling errors.

R=caryclark@google.com

Docs-Preview: https://skia.org/?cl=138542
Bug: skia:6898
Change-Id: Iba547873775a89f1d652be9b0219b84ffa8d0628
Reviewed-on: https://skia-review.googlesource.com/138542
Commit-Queue: Cary Clark <caryclark@skia.org>
Reviewed-by: Cary Clark <caryclark@skia.org>
Auto-Submit: Cary Clark <caryclark@skia.org>
diff --git a/docs/usingBookmaker.bmh b/docs/usingBookmaker.bmh
index 236c16d..f74db8f 100644
--- a/docs/usingBookmaker.bmh
+++ b/docs/usingBookmaker.bmh
@@ -118,6 +118,12 @@
 Install
 #A Go # https://golang.org/doc/install ##
  if needed.
+Check the version. The resuls should be 1.10 or greater.
+
+#Code
+$ go version
+##
+
 Get the fiddle command line interface tool.
 By default this will appear in your home directory.