fix iterating through paths that have spaces in them

Fixes #344, #196

test/exec.bats

@@ -0,0 +1,14 @@
+#!/usr/bin/env bats
+
+load test_helper
+
+@test "supports hook path with spaces" {
+  hook_path="${RBENV_TEST_DIR}/custom stuff/rbenv hooks"
+  mkdir -p "${hook_path}/exec"
+  echo "export HELLO='from hook'" > "${hook_path}/exec/hello.bash"
+
+  export RBENV_VERSION=system
+  RBENV_HOOK_PATH="$hook_path" run rbenv-exec env
+  assert_success
+  assert_line "HELLO=from hook"
+}