Ndradex

- Add `work_dir` option to `ndradex.run()` function
- user can specify the path of directory under which a temporary directory for intermediate files is created (automatically deleted after the function is finished)
- Update the method of QN string formatting
- [List of available LAMDA datafiles and transitions](https://github.com/astropenguin/ndradex/wiki/List-of-available-LAMDA-datafiles-and-transitions) is also updated for some molecules
- Update README
- Some refactoring in the LAMDA class

- Change the number of maximum iterations in RADEX (9999 → 999999)

- Fix the wrong behavior of `timeout` option
- in v0.1.5, `timeout` is used for **the entire** calculation
- now `timeout` is correctly used for a single RADEX calculation
- Rename progress bar option (`bar` → `progress`)
- Update the behavior of progress bar when keyboard interruption

- Add an option for toggling progress bar to `ndradex.grid.run()` function
- you can now disable to show the bar using `bar=False`

- Update README
- add basic documentation
- Update docstrings related to README

- Custom path of RADEX binary directory
- User can set an environment variable, `NDRADEX_BINPATH`, to specify the directory where RADEX binaries are placed.
- Note that this feature may be used only for development use and normal user don't need to set it up.
- Update MANIFEST.in
- Stop using `graft` because unnecessary files are possible to be included.