Yahooquery

-----
- Add :code:`valuation_measures` as a property to the :code:`Ticker` class.
Additionally, for Yahoo Finance premium subscribers, they can access the
:code:`p_valuation_measures` and supply either :code:`a`, :code:`q`, or
:code:`m` (annual, quarterly, monthly). The data returned with these can
be seen in the `Statistics` tab through the Yahoo Finance front-end.

.. image:: demo/valuation_measures.PNG

-----
- Fix bug in retrieving cash flow / income statement data. Most recent month was
combining with TTM. A new column was created in the dataframe called 'periodType'.
Annual data will be shown as '12M', quarterly data will be shown as '3M', and
trailing 12 month data will be shown as 'TTM'.

-----
- Fix timestamp conversion in the _format_data method of the _YahooFinance class

-----
- New Research class that allows a user with a premium subscription to retrieve
research reports and trade ideas from Yahoo Finance. List of trade ideas
through Yahoo Finance can be seen at: https://finance.yahoo.com/research/trade-ideas.
Research reports can be seen at https://finance.yahoo.com/research.

-----
- New Screener class that allows a user to retrieve predefined Yahoo
Finance lists. Some of these lists include most active, day gainers,
day losers, cryptocurrencies, and sectors / industries

-----
- Have Ticker class inherit from a base class, defined in base.py as
_YahooFinance. The base class contains the order of operations to
retrieve data (construct parameters, construct URLs, validate response,
and format the data).
- Yahoo login functionality, which allows a user to retrieve Premium data if they are a subscriber

- All available financials data (income_statement, balance_sheet, cash_flow)
- Company 360 (innovation score, significant developments, supply chain,
hiring statistics, and company outlook)
- Premium portal (research reports, trade ideas, technical events, value analyzer,
and company snapshots)
- Technical events
- Value analyzer (High-level value analysis)
- Value analyzer Drilldown (Detailed information about a symbol(s) value)
- Research reports
- Trade ideas

- New (free) data!

- news
- page_views
- recommendations
- technical_insights
- validation

- Change several properties and methods (get_endpoints -> get_modules,
all_endpoints -> all_modules)