Created parse_log.py, competitor to parse_log.sh
Take train loss from `Iteration N, loss = X` lines

Was previously using `Train net output #M: loss = X` lines, but there may not be exactly one of those (e.g., for GoogLeNet, which has multiple loss layers); I believe that `Iteration N, loss = X` is the aggregated loss.

If there's only one loss layer, these two values will be equal and it won't matter. Otherwise, we presumably want to report the aggregated loss.
Store data in lists of dicts and use csv package

Output format is unchanged (except that csv.DictWriter insists on writing ints as 0.0 instead of 0)
Merge pull request #1384 from CellScope/log-parser-python

Python log parser