First working example of program.

Very VERY ugly and probably not well optimized. Top level function
is read-mailfilter-file requiring a string with the name of the file.
Output is a list of hashes each containing regex (the regular expression
for the rule) and command(a lambda that has been curried with the maildir folder
destination and takes two additional args, currently stubbed out)

No error handling, all errors will crash the program.