Add arg handling for single-jira-pull

The first milestone I'm working towards is a standalone executable
which can pull a range of JIRA issues from a project.  This commit
adds some basic arg handling using getopt.  It also includes some
basic unit-tests for this functionality.  Typically I wouldn't unit
test this kindof stuff, but it was useful for two reasons:
    1/ This is my first real Python development, and this caught a
    surprising number of conceptual/scoping/etc problems.
    2/ It serves as a good refresher on the unittest module.

Required arguments for this single-jira-pull script are:
    --server: a URL for the JIRA instance to hit.
    --project: the project we want to pull issues from

Optional arguments for this script are
    --start: the number of the first JIRA issue to look for
    --end: the number of the last JIRA issue to look for
    --delay: a delay b/w requests.  Used to comply with robots.txt