Implement --output={null,pipe,<FILE>}

Fixes #377.

Cargo.lock

@@ -274,6 +274,7 @@ dependencies = [
  "csv",
  "indicatif",
  "libc",
+ "nix",
  "predicates",
  "rand 0.8.5",
  "rust_decimal",
@@ -356,6 +357,27 @@ version = "2.4.1"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "308cc39be01b73d0d18f82a0e7b2a3df85245f84af96fdddc5d202d27e47b86a"
 
+[[package]]
+name = "memoffset"
+version = "0.6.5"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "5aa361d4faea93603064a027415f07bd8e1d5c88c9fbf68bf56a285428fd79ce"
+dependencies = [
+ "autocfg 1.1.0",
+]
+
+[[package]]
+name = "nix"
+version = "0.24.1"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "8f17df307904acd05aa8e32e97bb20f2a0df1728bbc2d771ae8f9a90463441e9"
+dependencies = [
+ "bitflags",
+ "cfg-if",
+ "libc",
+ "memoffset",
+]
+
 [[package]]
 name = "normalize-line-endings"
 version = "0.3.0"