Fix for Windows: do not run binaries from CWD

This fixes a bug on Windows where `Command::new` would also run
executables from the current working directory, possibly resulting in
accidental runs of programs called `less`.

Cargo.lock

@@ -1,5 +1,7 @@
 # This file is automatically @generated by Cargo.
 # It is not intended for manual editing.
+version = 3
+
 [[package]]
 name = "adler"
 version = "1.0.2"
@@ -97,6 +99,7 @@ dependencies = [
  "error-chain",
  "git2",
  "globset",
+ "grep-cli",
  "lazy_static",
  "nix",
  "path_abs",
@@ -487,6 +490,23 @@ dependencies = [
  "regex",
 ]
 
+[[package]]
+name = "grep-cli"
+version = "0.1.6"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "2dd110c34bb4460d0de5062413b773e385cbf8a85a63fc535590110a09e79e8a"
+dependencies = [
+ "atty",
+ "bstr",
+ "globset",
+ "lazy_static",
+ "log",
+ "regex",
+ "same-file",
+ "termcolor",
+ "winapi-util",
+]
+
 [[package]]
 name = "hashbrown"
 version = "0.9.1"
@@ -1143,6 +1163,15 @@ dependencies = [
  "winapi",
 ]
 
+[[package]]
+name = "termcolor"
+version = "1.1.2"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "2dfed899f0eb03f32ee8c6a0aabdb8a7949659e3466561fc0adf54e26d88c5f4"
+dependencies = [
+ "winapi-util",
+]
+
 [[package]]
 name = "terminal_size"
 version = "0.1.16"