bump to v0.2.19

- codecov to 91%
- gocov to 93.7%
- reviewed all codes and fixed bugs
- fixed: data racing on SetNx/Set, and config files reloaded
- added: passwd input safely

bump to v0.2.17: fluent api style and more

- `--tree`;
- fluent api style;
- yaml/json/toml for config files loading/saving;
- `daemon.Enable()` was modified and improved;
- adds finder: FindSubCommand, FindFlag, FindSubCommandRecursive, FindFlagRecursive
- bugs fixed
- ...

v0.2.15

bumped to v0.2.15: fluent api; ToggleGroup; bugs fixed; golint;

bumped version to v0.2.11;

- add daemonization feature;
- add xref building hooks;
- add markdown generator;
- GetXXX(): duration, int slice;
- bugs fixed;

v0.2.9

bumped to v0.2.9: generating man page.

v0.2.7

to 0.2.7; fixed files/args not recognized

v0.2.5-pre

strict-mode for cmdr parsing; `ToggleGroup` not yet; `strHit`; fixed …

v0.2.5

ready for final