Nflgame

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- Player database updates.
- Changed the player update script to stay fresh on position and status
data (in addition to team data). Namely, if the attributes become
unavailable, then they should be empty, regardless of their previous
values.
- Changed the `csv` import to be local to the csv export function as a
bandaide for QPython on Android (see issue 32).
- Expose player identifiers as `gsis_id` in addition to `player_id`.

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- Data updates for preseason weeks 2-4 (4 isn't complete yet).
- A complete rewrite of the JSON player database. Meta data is
now much more complete (with the vast majority of every player
in nflgame data back to 2009 having some meta data). Also,
nflgame now includes a `nflgame-update-players` script to
update the JSON player database using a minimal number of
HTTP requests.
- Use `tsv` extension so GitHub shows test results better.
- Recover gracefully if there is a socket timeout when downloading
JSON data.

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- Mostly a maintenance release with some reorganization.
I'm beginning migration to a new documentation tool `pdoc`.

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- Fixed a bug where `nflgame.live` was not properly interpreting
the phase of the season. (It thought it was always the regular
season.) Now it should automatically infer preseason, regular
season or postseason.

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- Update schedule for the 2013 preseason and regular season.
- Updated the players.json meta data file.
- Added nflgame's first test. It compares aggregate statistics
from 2012 against statistics reported by Yahoo. Overall, the
prognosis is good, but there are definitely some inaccuracies.
But I do think `nflgame` is doing the best it can without
another source. Look in `test-data` for test results and look
in `scripts/compare-with-yahoo` for more details on the
methodology.
- Added some more team abbreviations from Yahoo. (Weird ones.)
- Added a method to player objects to guess their position
based on available statistics.
- Corrected a few typos (or artifacts from old names) in the
`nflgame.statmap` module.

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- Make the FieldPosition type constructor more accepting of
different inputs. e.g., an integer. Also, added an add_yards
method to FieldPosition that returns a new FieldPosition
with the given yards added to it.
- Make the default string representation of a game unambiguous.
- Modified the quarter numbering correction of drives to be
smarter by looking at all plays of a drive instead of just
the last one.
- Modified the play duplication logic to be heuristically smarter.
Namely, instead of just looking at play ids, nflgame now
inspects play data to see if two plays are semantically
equivalent. This was necessary because duplicate plays could
have different ids.
- Manually corrected some seriously corrupt data in the
Week 13 match up DET at NO. Also updated a couple other
games from 2012 with updates from upstream.
- Updated players.json with most recent player meta data.