Add support for TOML configuration files

[kupiakos]

This is used in many contexts, including being the format used by Cargo, the Rust package manager.

[codecov-commenter]

Codecov Report

Merging #144 (5c8c440) into master (af4d9cf) will not change coverage.
The diff coverage is 100.00%.

@@           Coverage Diff           @@
##           master     #144   +/-   ##
=======================================
  Coverage   48.41%   48.41%           
=======================================
  Files           2        2           
  Lines         252      252           
=======================================
  Hits          122      122           
  Misses        123      123           
  Partials        7        7           

Impacted Files	Coverage Δ
main.go	41.42% <100.00%> (ø)

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[kupiakos]

These lint errors seem unrelated and go fmt results in no change.

Error: StringData not declared by package unsafe (typecheck)
  Error: StringData not declared by package unsafe (typecheck)
  Error: StringData not declared by package unsafe (typecheck)
  Error: String not declared by package unsafe (typecheck)
  Error: String not declared by package unsafe (typecheck)
  Error: String not declared by package unsafe (typecheck)
  Error: a.Lock undefined (type *onceError has no field or method Lock) (typecheck)
  Error: a.Unlock undefined (type *onceError has no field or method Unlock) (typecheck)
  Error: a.Lock undefined (type *onceError has no field or method Lock) (typecheck)
  Error: a.Unlock undefined (type *onceError has no field or method Unlock) (typecheck)

[kupiakos]

@mco-gh is there anything blocking this?