Add filename to parsed clock entry list & provide a message when file exists assertion fails

[sshaw]

Could not get tests to run. Connection issues:

~/code/elisp/org-clock-csv >cask
error in process filter: Could not create connection to orgmode.org:443
~/code/elisp/org-clock-csv >make
"emacs" -batch -f package-initialize -l ert -L . -l org-clock-csv-tests.el -f ert-run-tests-batch-and-exit
Symbol's function definition is void: package-initialize