Parse --shell option value as shell command

Cargo.lock

@@ -243,6 +243,7 @@ dependencies = [
  "rust_decimal",
  "serde",
  "serde_json",
+ "shell-words",
  "statistical",
  "tempfile",
  "winapi",
@@ -680,6 +681,12 @@ dependencies = [
  "serde",
 ]
 
+[[package]]
+name = "shell-words"
+version = "1.0.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "b6fa3938c99da4914afedd13bf3d79bcb6c277d1b2c398d23257a304d9e1b074"
+
 [[package]]
 name = "statistical"
 version = "1.0.0"