[mod] handle indentation when previous is None
[mod] handle .indentation for inner node
[mod] finally, in 'if a: pass' pass.indentation == '' instead of '    '
[mod] make comment more readable
[mod] refactor, do all the same things in the same place to avoid confusion
[enh] handle all syntaxe cases
[enh] add utils folder
[enh] add indentation_test.py in utils folder
[doc] document .indentation
[mod] update TODO
[enh] start to implement get_indentation_node
[enh] new method node.get_indentation_node()
[enh] new method node.indentation_node_is_direct
[enh] start to implement nodelist.append_endl
[enh] nodelist.append_endl handle trailing correct endl node
[enh] nodelist.append_endl handle oneline expression
[mod] prepare planning
[enh] witnode.append_endl
[enh] same for classnode
[enh] same for funcdefnode