Chore: Respect Logging Pref of Parent/Supervisor App

[nelsonic]

As noted by @vans163 in #36 (comment) our current approach to logging
is a little crude and could result in a lot of noise and potentially even perf issues on a high traffic app. 💭

As highlighted in https://github.com/dwyl/envar/pull/36/files#diff-c24eb47ea99dc64a5109913f247d10fd83fa57e93cd9b4609cb703552215c901 there are 4 instances of Logger calls:

envar/lib/envar.ex

Lines 31 to 33 in 03b035d

	if is_nil(val) do
	Logger.error("ERROR: #{varname} Environment Variable is not set")
	end

envar/lib/envar.ex

Lines 55 to 58 in 03b035d

	case System.get_env(varname) do
	nil ->
	Logger.debug("#{varname} Environment Variable is not set")
	false

envar/lib/envar.ex

Lines 165 to 170 in 03b035d

	if File.exists?(path) do
	load(filename)
	else
	Logger.error("Required .env file does not exist at path: #{path}")
	:error
	end

envar/lib/envar.ex

Lines 199 to 202 in 03b035d

	def read(filename) do
	path = Path.join(File.cwd!(), filename)
	Logger.debug(".env file path: #{path}")

Most of these are conditional, i.e. they won't log if the variable is set or file exists.
But this last one ... I have to agree with @vans163 is sloppy. 🤦‍♂️

Todo

• Re-introduce Logs into the project but they should:
  • Be OFF by default i.e. not noisy! [they can be enabled on :dev or :test]
  • Respect the Logging level of the "parent" (e.g. Phoenix) App.

Side Quest: