Escape backticks in --help.

Otherwise --help will try to run those quote things as commands in the
shell. Oops!

run_test_suite

@@ -84,12 +84,12 @@ Options for '@product' features:
 Note that '@source' features has no relevant options.
 
 CUCUMBER_ARGS can be used to specify which features to be run, but also any
-cucumber option, although then you must pass `--` first to let this wrapper
+cucumber option, although then you must pass \`--\` first to let this wrapper
 script know that we're done with *its* options. For debugging purposes, a
 'debug' formatter has been added so pretty debugging can be enabled with
-`--format debug`. You could even combine the default (pretty) formatter with
-pretty debugging printed to a file with `--format pretty --format debug
---out debug.log`.
+\`--format debug\`. You could even combine the default (pretty) formatter with
+pretty debugging printed to a file with \`--format pretty --format debug
+--out debug.log\`.
 "
 }