Add a few messages to Makefile to help noobs
Clean up .dtl.erl files with `make clean`
Remove error running `make clean` when is clean.
Fix typo about R16B03
Fix module_older_than when file not exists. Also..

Also remove unnecessary calendar:datetime_to_gregorian_seconds
conversion. Comparing datetime tuples should be sufficient, and also
automatically handles the case where a file is not found, since
filelib:last_modified returns `0` if the file is not found.

Also add a a few try-catch blocks:

1) To boss_load:compile_view_dir_erlydtl, where erlydtl:compile_dir was
crashing due to directory-not-found error.  This may not need to be
permanent, since it's contingent on a fix in erlydtl, but without it
right now, CB doesn't work.

2) To boss_web_controller_handle_request:handle_request/3, where a crash
was silently failing rather than producing an error message in any log.
It will now generate an appropriate lager error message so it can
be debugged.
Merge branch 'master' of https://github.com/choptastic/ChicagoBoss