CLI

Adds a CLI and IPython magic for zipline.

CLI example:
```
python run_algo.py -f dual_moving_avg.py --symbols AAPL --start 2011-1-1 --end 2012-1-1 -o dma.pickle
```
Grabs the data from yahoo finance, runs the file dual_moving_avg.py (and looks for dual_moving_avg_analyze.py which, if found, will be executed after the algorithm has been run), and outputs the perf dataframe to dma.pickle.

IPython magic command (at the top of an IPython notebook cell):
```
%%zipline --symbols AAPL --start 2011-1-1 --end 2012-1-1 -o perf
```
Does the same as above except instead of executing the file looks for the algorithm in the cell and instead of outputting the perf df to a file, creates a variable in the namespace called `perf`.