Feature/rspec doc title

[Haniyya]

This enables the extractor to record doc_titles from an RSpec example.
This information is currently not used but it will be in #4 .

The changes are heavily inspired by Apipie#445 and @ghost s solution.

[stex]

NB: When using a alias_example_to to record basic apipie examples, it will silently discard additional metadata if no example name is given (or rather use the metadata as example name I guess).
Therefore, an example name has to be given.

# rails_helper.rb
config.alias_example_to :apipie_example, :show_in_doc

# No title recorded (as none was given)
apipie_example do

# Title recorded
apipie_example 'I am name', doc_title: 'Something' do

# Not title recorded even though it seems one was given
apipie_example doc_title: 'Something'