moved period outside parentheses
updated paragraph on concurrency
added an also
updated paragraph on parentheses in Clojure
switched a colon to a semicolon
updated first paragraph about the REPL
clarified second paragraph about the REPL
added quotes in the third paragraph about the REPL
added code formatting in basic arithmetic exercise
replaced colon
added an and
changed spacing around em dashes
Merge pull request #48 from kpfell/intro-to-clojure-corrections

"Intro to Clojure" modifications