Javaproperties

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- `parse()` now accepts strings as input
- **Breaking**: `parse()` now returns a generator of custom objects instead of
triples of strings
- Gave `PropertiesFile` a settable `timestamp` property
- Gave `PropertiesFile` a settable `header_comment` property
- Handle unescaping surrogate pairs on narrow Python builds

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- Require `javaproperties` 0.6.\*
- Use `'javapropertiesreplace'` error handler when opening output files
- Gave `javaproperties`' `format`, `select`, and `set` subcommands `--ascii`
and `--unicode` options for controlling the escaping of non-ASCII characters
in output
- Gave `properties2json` and `json2properties` `--ascii` and `--unicode`
options for controlling the escaping of non-ASCII characters in output
- `properties2json` now always outputs UTF-8
- By default, comments output by `json2properties` now have all non-ASCII
characters escaped rather than all non-Latin-1 characters

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- Added an example of each format to the format descriptions in the docs
- Fix building in non-UTF-8 environments

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- **Bugfix**: `java_timestamp()` now properly handles naïve `datetime` objects
with `fold=1`
- Include installation instructions, examples, and GitHub links in the Read the
Docs site

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- Include installation instructions, GitHub links, and changelog in the Read
the Docs site
- Gave `json2properties` a `--comment <comment>` option
- Support Python 3.8

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- Drop support for Python 2.6 and 3.3
- Support `javaproperties` 0.5.0