Skip comments and blanks in dictionary files

[skangas]

This allows using comments and blank lines in dictionary files. My use case is that I have a file like the following:

# submit upstream
sceanrios->scenarios
eamcs->emacs
sccopes->scopes
# emacs specific
brunches->branches
ecmacs->emacs
ehsell->eshell
[...]

[skangas]

The code coverage test seems to be failing. I'll take a closer look if this feature is considered acceptable.