refs #281. Replaces hardcoding of virtualenv python executable with sys.executable.
refs #281. Changes fetch_tweets_by_id to fetch in bulk instead of one at a time.
Revert "refs #281. Changes fetch_tweets_by_id to fetch in bulk instead of one at a time."

This reverts commit 75bdb25152445d862952a97fc6e04fc7243c9820.
Changes strategy to use ENV in wsgi.py if present to build executable path, otherwise use sys.executable.
Merge pull request #282 from gwu-libraries/ticket_281

refs #281. Replaces hardcoding of virtualenv python executable with sys....