Added unit test.
Fixed sage-shell:development-version.
Modified sage-shell-help:file-type-make-button.
Fix indentation
If a link to a file is pressed in the doc buffer, then it opens a file in
src by default.
Create links to source files in the output if an error is raised.
recenter when visit a file through a button.
make error links in the doc buffer.
Use noflet for test.
modified sage-shell:sage-root and sage-shell:sage-executable.
make a link to pyx file.
Modified sage-shell-help:file-type-make-button.
Fixed sage-shell:make-err-link--line-regexp.
Fixed sage-shell-help:file-type-make-button.
Create a link to a pxy file in error line.
refactoring
Renaming.