add streaming analytics doc page
edits to streaming-analytics doc page
edits to streaming analytics doc page

Suggested by (and often copied verbatim from) @eigenhombre
add semicolons to SQL commands
correct join input order
remove redundant sentence
spellcheck
replace first, second with lambda x: x[1/2]
edits from writing blogpost
streaming-analytics edits suggested by @eriknw
fix link
add imports, map.get -> pluck
Merge pull request #186 from mrocklin/streaming-analytics-doc

Add streaming analytics doc page