feat: Deprecate camel case functions
Originally, `unittest` was modeled after Python standard library. So it
used setup function names same as the Python equivalents.
Mixing naming conventions has little sense, so I will gradually standardize
the naming conventions in user-friendly way.

feat: Update help message

fix: Better color support detection
Color support detction is based on TERM environmental variable. On Github
Actions CI environments TERM is not set which generates error messages.
We should assume, that this kind of terminal is a basic one (dumb terminal).
Fixes: #11

fix: Incorrectly recognized test function
Variables name started with `test_` shouldn't be treated as a test cases.
Fixes: #8

fix: Invalid split of error msg
Fixes SC2145 "Argument mixes string and array". Also fixes error message.

fix: Invalid format of debug message
Change efdc06f introduced bug: indented debug description prints escaped
characters.
I'm not sure if `%b` format is portable, so I disable shellcheck rule. I also
introduce CLICOLOR_FORCE env var, for testing purposes (more info:
https://bixense.com/clicolors/).
Fixes: #9

refactor: Remove shellcheck warnings
Fixed:
- SC1090 Can't follow non-constant source.
- SC2013 To read lines rather than words, pipe/redirect to a while read loop.
- SC2046 Quote this to prevent word splitting.
- SC2059 Don't use variables in the printf format string.
- SC2086 Double quote to prevent globbing and word splitting.
- SC2181 Check exit code directly.

feat: Drop extension from name
With shebang extension is unnecessary.

feat: Version 0.1-dev