updates

doc/src/tut/classes.do.txt

@@ -17,14 +17,8 @@ notify a coordinate system. Here is an example where we
 draw $x$ and $y$ axis of three coordinate systems of different
 rotation:
 
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 FIGURE: [fig-tut/Axis, width=500 frac=0.7]
 
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 The corresponding code looks like this:
 
 @@@CODE ../../../pysketcher/tests/test_pysketcher.py fromto: def test_Axis@drawing_tool.savefig\('tmp_Axis'\)
@@ -37,15 +31,8 @@ a distance in a sketch, with an additional text in the middle of the arrow.
 The figure
 
 
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 FIGURE: [fig-tut/Distance_wText, width=500 frac=0.7]
 
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 was produced by this code:
 
 @@@CODE ../../../pysketcher/tests/test_pysketcher.py fromto: def test_Distance_wText@drawing_tool.savefig\('tmp_Distance
@@ -58,9 +45,6 @@ the appearance of the text that goes with the distance arrow.
 
 FIGURE: [fig-tut/Rectangle, width=500 frac=0.7]
 
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 The above figure can be produced by the following code.
 
 @@@CODE ../../../pysketcher/tests/test_pysketcher.py fromto: def test_Rectangle@drawing_tool.savefig\('tmp_Rectangle
@@ -73,9 +57,6 @@ to the geometry of the current shape.
 
 FIGURE: [fig-tut/Triangle, width=500 frac=0.7]
 
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 The code below produces the figure.
 
 @@@CODE ../../../pysketcher/tests/test_pysketcher.py fromto: def test_Triangle@drawing_tool.savefig\('tmp_Triangle
@@ -88,9 +69,6 @@ to the location of the p1, p2, and even p3 texts.
 
 FIGURE: [fig-tut/Arc, width=400 frac=0.5]
 
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 An arc like the one above is produced by
 
 @@@CODE ../../../pysketcher/tests/test_pysketcher.py fromto: def test_Arc@drawing_tool.savefig\('tmp_Arc
@@ -99,9 +77,6 @@ An arc like the one above is produced by
 
 FIGURE: [fig-tut/Spring, width=800 frac=1]
 
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 The code for making these two springs goes like this:
 
 @@@CODE ../../../pysketcher/tests/test_pysketcher.py fromto: def test_Spring@drawing_tool.savefig\('tmp_Spring
@@ -110,9 +85,6 @@ The code for making these two springs goes like this:
 
 FIGURE: [fig-tut/Dashpot, width=600 frac=0.8]
 
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 This dashpot is produced by
 
 @@@CODE ../../../pysketcher/tests/test_pysketcher.py fromto: def test_Dashpot@drawing_tool.savefig\('tmp_Dashpot
@@ -126,14 +98,8 @@ Looks strange. Fix x axis.
 The `StochasticWavyCurve` object offers three precomputed
 graphics that have a random variation:
 
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 FIGURE: [fig-tut/StochasticWavyCurve.png, width=600 frac=1]
 
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 The usage is simple. The construction
 
 !bc pycod