Using air for testing

[skelouse]

Here I implemented a simple way to test and hot-reload with air while also indicating testing build flags, a specific test, etc without having to create a config. I'm inclined to improve it on there unless there is a want to add an air test command to this package.

Essentially air test <args...> would take the arguments and dump them into a config as:

[build]
  cmd = "go test <args...>"

Current usage examples can be found in the README:

# Livereload a test using air, see: https://github.com/cosmtrek/air
# Note: be sure you have air installed `which air` => ~/go/bin/air

# Simple Live reload of all relative tests
$ asd air

# Matcher Live reload equivalent to `go test -v --run <some-test>
$ asd air <some-test>

# Live reload of all tests below a given directory equivalent to `go test -v ./...`
$ asd air ./...

[skelouse]

I just updated my air install and noticed there are arguments to update the config strings, but the use case below does not work as flags are parsed by air:

`air -build.cmd go test -v --run <TestToRun>`

[makiuchi-d]

arelo is the right choice for your usage:

arelo -p '**/*.go' -i '**/.*' -- go test -v --run <TestToRun>