Fixes TextCorpus not having proper metadata info.

I've defaulted to returning the line number that a document appears on.
update CHANGELOG with new pull requests
Support for matrix-valued topic/word prior eta in LdaModel. Allows topics to be seeded with specific words
TextCorpora no longer raises exception on empty input file
Fix length for corpora on empty files
Remove commented out lines
Merge pull request #203 from cscorley/fix_textcorpus_metadata

Fixes TextCorpus not having proper metadata info (rebased)
PEP8 corpora changes
Add description to CHANGELOG.txt
Merge pull request #209 from cscorley/empty_corpora_inputs

Fix length calculation for corpora on empty files
Refactor corpus tests

Also ensures that all possible temp test files are removed

Use overriden run instead of skipTest (for Python 2.6 support)
Merge pull request #210 from cscorley/simplify_tests

Refactor corpus tests
unicode fix in non-binary word2vec load
doc fixes
Fix saving unicode-based corpora to Mallet/Low format
Added ability to specify token map in Dictionary.from_corpus

In cases where the BOW matrix is given along with an id -> token map,
this feature allow for a perfect reconstruction of the dictionary
object using the from_corpus method.
Use a dictlike structure for id -> token mapping
minor reformat
remove obsolete comment
update docs re. unicode/utf8 tokens
* now both accepted on input; unicode stored internally