Refactor Navigator class and spec to define page getter dynamically
Update scraper to use Navigator products_page method
Charge class is responsible for initialize it's own data
Scraper uses create_month_charges method only
Dynamically dispatch Navigator methods in Scraper
Update Charge spec
Change name from HTMLParser to Parser
Charge class is responsible for creating charge objects
Charge class calculates month summary directly
Add methods current_month_summary and last_month_summary to Scraper