Add directions + package description to usage/index docs

docs/usage.rst

@@ -5,3 +5,39 @@ Usage
 To use Tiingo Python in a project::
 
     import tiingo
+
+Now you can use the ``TiingoClient`` to make your API calls. (Other parameters are available for each endpoint beyond what has been written below, see docs for full details.)
+
+.. code-block:: python
+
+   from tiingo import TiingoClient
+   # Set TIINGO_API_KEY in your environment variables in your .bash_profile, OR
+   # pass a dictionary with 'api_key' as a key into the TiingoClient.
+
+   # With environment variable
+   client = TiingoClient()
+   # With hardcoded dictionary key
+   client = TiingoClient({'api_key': "MY_SECRET_API_KEY"})
+
+   # Get Ticker
+   # See official docs for list of all supported tickers + date ranges
+   ticker_metadata = client.get_ticker_metadata("GOOGL")
+
+   # Get latest prices, based on 3+ sources, as CSV or JSON, sampled weekly
+   ticker_price = client.get_ticker_price("GOOGL", frequency="weekly")
+
+   # WARNING: These will only work if your account has access to the 
+   # Mutual Funds portion of the API.
+   # Get mutual fund metadata
+   fund_metadata = client.get_fund_metadata("VFINX")
+   # Get mutual fund Expenses and Shareholder Fee Data for June 2017
+   fund_metrics = client.get_fund_metrics("VFINX", "2017-06-01", "2017-06-30")
+
+   # Get news articles about given tickers or search terms from given domains
+   # Coming soon!
+
+Further Docs
+--------
+
+* Official Tiingo Documentation: https://api.tiingo.com
+* Tiingo-Python Documentation (Under Construction): https://tiingo-python.readthedocs.io.