Integrate update notifier (#202)
Warnings should be on stderr, not stdout
Output the update notice on stderr so as not to interfere with the actual output of the commands
Use unsafeCleanup to clear temporary dirs, closes #345.
Merge pull request #386 from twitter/tmp-dir-cleanup

Use unsafeCleanup to clear temporary dirs, closes #345.
Merge pull request #384 from wibblymat/warn-on-stderr

Warnings should be on stderr, not stdout
Merge pull request #383 from wibblymat/update-notifier

Integrate update notifier (#202)
Update travis image to master.
Fix typo in README
Fix typo and language in README