Unit test framework

[umitanuki]

Each algo code should be easily unit tested. The concept of unit test is not very known to the type of users here. Rather than asking them to build their own unit test, we should provide some high level template that does:

• provide local fake backend
• provide fast replay executor
• use real (past) market data
• with a pre-defined small set of symbols, simulate a (constant) day using the historical data quickly, basically smoke test to catch any issues like typo.

[umitanuki]

Although partially, it is now supported to run smoke testing with #21

[shlomiku]

I will add a pylivetrader command called smoke
it will have 2 options:

1. generate a smoke test file for a gived algorithm
   2.. it will execute the generated smoke test upon the user's algorithm

so the workflow will be as such:
pylivetrader smoke generate --in-file algo.py --out-file smoke_algo.py
and execution will be
pylivetrader smoke run -f smoke_algo.py

or something similar