stablerange: introduce an 'basicstablerange'
This class hold all the basic of stable range but the part specific to the
sorting.
This allow to clearly express what is expected from each method and to generate
tests output to be validated against the more complex implementation.
While writing this, we spotted a bug in the current stable range implementation.
Fix coming.
Doc is generated with sphinx.
You can generate the doc with:
```
make
```
# Tutorials
For updating the tutorials, you need to have the docgraph extension installed
(https://pypi.python.org/pypi/hg-docgraph).
Then run the test-topic-tutorial.t and test-tutorial.t to update the output if
needed.
You'll need the dot binary (likely installed by the graphviz package in your
package manager) in order to have graphviz graphs rendered in the html output.
Simply run make in the docs directory should takes care of the conversion of
the tutorial .t files into .rst files. Then sphinx should do the rest of the
jobs by rendering graphviz graphs.