Update README.md

Adds gitattributes to ignore notebooks from language stats

Minor cleanup to demo notebook

Adds mallet models to repo

Renames models package to news_analyze

Adds trained lda model to repo

Removes HN Analysis notebook from repo

Minor fixes to text in demo notebook

Updates demo notebook with introduction, more detailed explanations and conclusion

uses a uniform value of 85 for threshold percentile for topic similarity values

Adds method to plot topic article distributions, sorts clustered matrix in order of cluster quality

prints topic table when displaying the popularity trend of a topic

clearly shows article content has been trimmed while printing article

computes cluster silhouette scores for cluster quality and prints highest quality clusters first

prints standalone and common topics separately when printing clusters for ease of reading