add a User-Agent header to request

rss2jira was blocked from accessing seqanswers.com because their CDN,
CloudFlare, does a "Browser Integrity Check".
switch to WatchedFileHandler

Switch to WatchedFileHandler so the daemon's log can be rotated by
external tools such as 'logrotate'.
bump version to 1.1.21
Merge pull request #3 from nnutter/master

v1.1.21 - Better Log Handling and Now Specifies a User-Agent