Silencing FactoryGirl's tranient warning

This PR silences FactoryGirl's transient warning:

```bash
DEPRECATION WARNING: `#ignore` is deprecated and will be removed in 5.0. Please use `#transient`
instead. (called from block (3 levels) in <top (required)> at /Users/adomokos/Programming/Rails/oss/cfp-
app/spec/factories/people.rb:37)
```