chore(library/standard): fix permission
chore(Makefile): add and use extract_deps in Makefile
chore(library/standard/extract_dep): add EXCEPT to specify deps which do not need compilation
fix(library/standard/equality_test): add "import kernel"
fix(library/standard/list): use nat instead of Nat
fix(library/standard/extract_deps): took out sed
doc(README.md): add travis-ci badge
feat(nat): more theorems for le and lt