+ start testing new execution system.
+ more stdin tests.
+ one small test for _out, one big achievement for unittesting...
+ two more tests for None handling.
* finally start getting rid of sh.
- all code that went around sh's classes.
* o, Capture and CommandFailed mover to ayrton.execute.
+ CommandNotFound in ayrton.execute.
* lots of s/ayrton.CommandWrapper/ayrton.execute.Command/.
+ close the reading file before stopping the iteration of the lines read.
- all the tests moved to test_execute.py.
+ test for reading lines from a captured output.
+ first stderr tests.
+ more passing tests.
+ even more passing tests.
+ readlines().
+ test the first step towards echo()|grep().