[TwitterApplication]:

Modified TwitterApplication so that it reads the access tokens and
coordinates from shell environment variables, which allows the same
harvesting program to be configured to collect from different geographical
coordinates, and use a different twitter account to the other harvesters.
[collect-tweets.sh]:

Added a shell script to invoke the harvester. I suggest not adding the
files containing the account tokens and coordinates, because we will need
several different ones, for each individual harvesting node.