Tldr.py

- support relative path for download path
- add install script
- fuzzy find support(with grep or fzf)
- drop 3.3/3.4 support, add 3.6+ support

- support the new syntax, 22

- support search commands in other platforms, 20

- support locate the command page, 11

- support custom the configuration file via `TLDR_CONFIG_DIR`, 9

- support rebuild the index(8), and rebuild the index after updating
- improve tests, 12