Merge pull request #5 from derek-dchu/backtest

Add script for creating valid tickers.
separated Blocks to separate file, completely redefined thresholds and conditions
made volatility block class
covariance class
separated BT further, built conditions and ready for asset and portfolio models
added logic to score survivors of thresholds
running code with blocks and statuses
took out white space in objects
refactored the code with Derek :)
taking out whitespace in dictionariy
ordered dates in dates in range
asset and algorithm models save in backtest.py
Merge pull request #6 from lucasbrambrink/backtest_dev

Backtest dev to backtest
changed 365 to 252 trading days in one year, and changed logic in case algorithm returns 0 stocks to buy -- do nothing
fixed frequency calculation , dates_in_rage contained duplicates
preparing risk metric calculator for backtesting
added method to seed risk free yields into DB and started working on Risk Metrics Calculator
added risk calculator, needs to be debugged but general framework established
risk metrics get calculated, need to find a way to double check the values
fixed the rmc, values seem to be right but needs proper testing