Fulltext extraction improvement #1

[codelucas]

Full-text extraction improvements from this diff:

• <li> and <ul> list elements were usually filtered out in the old extraction mechanism, the new updated extraction code includes list elements (and even in their original form, newlines are inserted!)
• Random paragraphs, usually heading or ending, in an article were filtered out because of a strict extraction mechanism. Changes were made to make the mechanism more lenient.

Case 1:
URL: http://lungcancer.about.com/od/Targeted-Therapy-Lung-Cancer/fl/Genetic-Testing-for-People-with-Lung-Cancer.htm?utm_source=google&utm_medium=social&utm_campaign=shareurlbuttons
Fail description: Before this PR, titles and lists <li><ul> elements were flat out ignored in the output fulltext. Also, the intro paragraph (huge) was ignored for no good reason.
Before: https://dl.dropboxusercontent.com/u/103212767/old_fulltext/about.com2.txt
After: https://dl.dropboxusercontent.com/u/103212767/new_fulltext/about.com2.txt

Case 2:
URL: http://in.reuters.com/article/2014/12/30/india-sensex-nifty-idINKBN0K80A020141230
Fail description: First paragraph of all Reuters articles are ignored for no good reason.
Before: https://dl.dropboxusercontent.com/u/103212767/old_fulltext/reuters.com1.txt
After: https://dl.dropboxusercontent.com/u/103212767/new_fulltext/reuters.com1.txt

Case 3:
URL: http://www.telegraph.co.uk/news/worldnews/asia/indonesia/11315001/AirAsia-plane-reported-missing-with-162-passengers-onboard-latest.html
Fail description: Old extractor drops random blocks of text: for example, the timestamp "07.13" is dropped and many tweets about the flight crash were also dropped (embedded tweets are becoming more commonplace within articles and should be included)
Before: https://dl.dropboxusercontent.com/u/103212767/old_fulltext/telegraph.co.uk1.txt
After: https://dl.dropboxusercontent.com/u/103212767/new_fulltext/telegraph.co.uk1.txt

[codelucas]

Excuse commits 4d2b68b, 2b4d2bc and e54b6ab, I included too many code changes in the commit and wanted to amend and split the commit.

[codelucas]

@amontalenti
NOTE: The important (full-text algorithm changing) diffs in this PR are:
7697eb0
05fd1aa