Merge pull request #11 from jptiancai/master

support python version 2.6+
Update README.md
Merge pull request #12 from jptiancai/patch-1

Update README.md
添加对于任务 section header 的 support
make the `append section title` feature configurable
fix conflict
extract pretty_print_scheduled_tasks
添加显示所有人总工时的功能
display the man status in fixed order
change task name separator to dash
支持多级 section title
增加关于支持任务多级细分的示例
remove useless task_id feature
extract parse_task_line
update_headers -> parse_header_line
minor text change
extract parse_vacation_line
minor
minor
enrich the content of summary