v0.3.0

Added support for expandable named placeholders.

- `%(NAME)*s`, `%(NAME)*q` expand named values as array items.
- `%(NAME)**s`, `%(NAME)**q` expand positional values as key value pairs.
- Pass values for named array items using `NAME=ITEM_N` syntax.
- Pass values for named key value pairs using `NAME=KEY_N NAME=VALUE_N` syntax.

Also, changed the syntax for optional placeholder from `$?(...)` to `$(...)?`.

v0.2.7

- Added support for optional placeholders.
  ```bash
  jf "{str_or_bool: %?(str)q %?(bool)s, optional: %?(optional)q}" str=true
  # {"str_or_bool":"true","optional":null}
  ```

- Added support for placeholders with variable length values.
  ```bash
  jf [%*s] 1 2 3
  # [1,2,3]

  jf {%**q} one 1 two 2 three 3
  # {"one":"1","two":"2","three":"3"}
  ```

- Generate manpage.

Fixed another bug related to default values

To reproduce: `jf "%(foo=bar)q: %(foo)q"`
Should fail, but gave `{"bar":"bar"}`

Fail for incomplete named placeholder

Fix linting

Support default values (#2)

* Support default values

* Improve usage error

* Cleanup readme

Use %v to print jf version

Update version

Optimize release

Bump for binary release