Fix example code in README

[tricknotes]

• A method that has ? suffix should return boolean, but this method return an object that respond to valid?.
• All other examples don't have ?.

  • scientist/README.md

    Line 44 in 8d9fd4e

    experiment.use { model.check_user(user).valid? } # old way

  • scientist/README.md

    Line 152 in 8d9fd4e

    e.use { model.check_user(user).valid? }

  • scientist/README.md

    Line 167 in 8d9fd4e

    e.use { model.check_user(user).valid? }

  • scientist/README.md

    Line 251 in 8d9fd4e

    e.use { model.check_user(user).admin? }

  • scientist/README.md

    Line 498 in 8d9fd4e

    e.use { model.check_user(user).valid? } # old way

  • scientist/README.md

    Line 553 in 8d9fd4e

    e.use { model.check_user(user).valid? }

[franzliedke]

Good catch!