add middlelevel getter/parser/formetter.
use load_buffer as string loader. fix map bug. move typedef to Types.
WIP: some implementation

update Const instances.
change directory structure.
add xpath methods.
binding complete.
highlevel API
change Modify monad.
some changes.

change class structure.
add travis.
add documentation.
add small test.
add forgetNodeKind. add Show instance to NodeSet. fix c-source.
add README.md
Merge branch 'pre-initial'