Fix fd leak noticed by Barry Haddow
Fixed issue with lost back-off weights
Second attempt at fixing missing back-off issue
More verbose exception for duplicate n-gram detected
Merge branch 'master' of github.com:kpu/kenlm
Require that words in higher-order n-grams have been seen in the vocabulary (or be <unk>).
Also change test cases because this did not apply for the word "good" in the test ARPA file.
BUGFIX: some unigrams were being read incorrectly.

By design, FilePiece invalidates any previous StringPiece when a new read happens.  Read1Gram was reading the vocab word, reading the backoff, and then
using the vocab word.  This ordering was incorrect and led to occasional vocab issues.

Stephan Peitz saw this as a duplicate n-gram detected error since words were mapping to OOV.
Pull in minor changes from Moses
minor changes to allow scoring with NullState
const
Allow fallback discounts.  Mostly for class-based LMs, but users have to make up the values.
Remove Marcin's debug message "Pruning"
Newline in warning
Fix test (arguments changed)
Enable interpolate_unigrams by default
WordIndex was missing namespace in pxd, returning OOV count with
full_scores
Isolate prob+backoff vs q computation
Merge remote-tracking branch 'upstream/master'
Fix implicit discount_fallback to be a vector of strings
including oov to python example use of full_scores