Add gh-pages.mk.
Update depeloper.md.
Bug fixed.
Merge pull request #124 from kenbeese/create-gh-pages

Upload API Reference
Minor change in document.
Add prefix_path filter and its test.
Add 'change_path' and its test.
Add pipes 'move_node' and 'change_path' and its test.
Some documents are changed and minor bugs are fixed.
Add exception of from_path.
Change conditional branches.