remove OOP interfaces
update libgit2 v0.20.0
wip
update readme
add config
[config] add parse
wip
add stubs
[repository] implement several functions
[object] implement several functions
[index] implment several functions
add several stubs
[revparse] implement functions
[git_status_list] add stub codes
[git_status_list] add stub codes
ad branch and tag
[remote] add stubs
add several stubs
fix warnings
[ignore] add functions