Add Quora QA dataset (#2)

list.json

@@ -1,5 +1,12 @@
 {
 	"corpora": {
+		"quora-duplicate-questions": {
+			"description": "over 400,000 lines of potential question duplicate pairs. Each line contains IDs for each question in the pair, the full text for each question, and a binary value that indicates whether the line truly contains a duplicate pair.",
+			"checksum": "d7cfa7fbc6e2ec71ab74c495586c6365",
+			"file_name": "quora-duplicate-questions.gz",
+			"source": "https://data.quora.com/First-Quora-Dataset-Release-Question-Pairs",
+			"parts": 1
+		},
 		"wiki-en": {
 			"description": "Extracted Wikipedia dump from October 2017. Produced by `python -m gensim.scripts.segment_wiki -f enwiki-20171001-pages-articles.xml.bz2 -o wiki-en.gz`",
 			"checksum-0": "a7d7d7fd41ea7e2d7fa32ec1bb640d71",