Fix in callbacks and tutorials.

docs/src/tutorials/.gitignore

@@ -0,0 +1 @@
+*.html

docs/src/tutorials/README

@@ -1,6 +1,6 @@
 All tutorials should be written or edited as .ipynb files.
 
-The script in ./build.sh will convert these to .jl and .md files.
+The script in ./build.sh will convert these notebooks to [.jl, .md, .html].
 
 If .md files should contain output, make that the .ipynb notebooks have
 been executed, either through the browser or command-line `jupyter`.

docs/src/tutorials/build.sh

@@ -16,6 +16,7 @@
 
 for x in $(ls *.ipynb); do
     python -m jupyter nbconvert --to markdown $x
+    python -m nbconvert --to html $x
     python -m jupytext --to jl $x
 done