doc: delete go course notes

They're out of date, a pain to maintain, and most of the material
is better served by the Go Tour.

Fixes #2101.

R=golang-dev, rsc, r, adg
CC=golang-dev
https://golang.org/cl/5489053

doc/docs.html

@@ -33,17 +33,6 @@ concepts: syntax, types, allocation, constants, I/O, sorting, printing,
 goroutines, and channels.
 </p>
 
-<h3 id="course_notes">Course Notes</h3>
-<p>
-Slides from a 3-day course about the Go programming language.
-A more thorough introduction than the tutorial.
-</p>
-<ul>
-<li><a href="GoCourseDay1.pdf">Day 1: Basics</a> <small>[270KB PDF]</small></li>
-<li><a href="GoCourseDay2.pdf">Day 2: Types, Methods, Interfaces</a> <small>[270KB PDF]</small></li>
-<li><a href="GoCourseDay3.pdf">Day 3: Concurrency and Communication</a> <small>[180KB PDF]</small></li>
-</ul>
-
 <h3 id="effective_go"><a href="effective_go.html">Effective Go</a></h3>
 <p>
 A document that gives tips for writing clear, idiomatic Go code.

doc/go_tutorial.html

@@ -15,11 +15,8 @@ After you've read this tutorial, you should look at
 <a href='/doc/effective_go.html'>Effective Go</a>,
 which digs deeper into how the language is used and
 talks about the style and idioms of programming in Go.
-Also, slides from a 3-day course about Go are available.
-They provide some background and a lot of examples:
-<a href='/doc/GoCourseDay1.pdf'>Day 1</a>,
-<a href='/doc/GoCourseDay2.pdf'>Day 2</a>,
-<a href='/doc/GoCourseDay3.pdf'>Day 3</a>.
+An interactive introduction to Go is available, called
+<a href='http://tour.golang.org/'>A Tour of Go</a>.
 <p>
 The presentation here proceeds through a series of modest programs to illustrate
 key features of the language.  All the programs work (at time of writing) and are

doc/go_tutorial.tmpl

@@ -11,11 +11,8 @@ After you've read this tutorial, you should look at
 <a href='/doc/effective_go.html'>Effective Go</a>,
 which digs deeper into how the language is used and
 talks about the style and idioms of programming in Go.
-Also, slides from a 3-day course about Go are available.
-They provide some background and a lot of examples:
-<a href='/doc/GoCourseDay1.pdf'>Day 1</a>,
-<a href='/doc/GoCourseDay2.pdf'>Day 2</a>,
-<a href='/doc/GoCourseDay3.pdf'>Day 3</a>.
+An interactive introduction to Go is available, called
+<a href='http://tour.golang.org/'>A Tour of Go</a>.
 <p>
 The presentation here proceeds through a series of modest programs to illustrate
 key features of the language.  All the programs work (at time of writing) and are