more specific error when directory-ness mismatches
die early when a file to be diffed doesn't exist
cfg option for skipping browser open on reload
default to not opening browser tabs on reloads
kill cfg option for browser reloading
Merge pull request #19 from ryan-williams/skip-browser-reload

cfg option for skipping browser open on reload
cleaner error msg printing
Merge pull request #22 from ryan-williams/errors

Die early when a file to be diffed doesn't exist
pass ORIGINAL_DIR down to reloader thread