Add a benchmark driver and a simple benchmark

This adds a simple script that drives benchmarks, and a simple sample
benchmark.

benchmarks/benchmarks/seq_echo.fish

@@ -0,0 +1,3 @@
+for i in (seq 1000)
+   echo $i
+end

benchmarks/driver.sh

@@ -0,0 +1,14 @@
+#!/bin/sh
+
+if [ "$#" -ne 1 ]; then
+    echo "Usage: driver.sh /path/to/fish"
+fi
+
+FISH_PATH=$1
+BENCHMARKS_DIR=$(dirname "$0")/benchmarks
+
+for benchmark in "$BENCHMARKS_DIR"/*; do
+    echo $(basename "$benchmark")
+    ${FISH_PATH} --print-rusage-self $benchmark > /dev/null
+done
+