Dependence of find_weekday() on calcuate_date()

[iliakur]

Currently, if we run the find_weekday() method without first running the
calculate_date() one we will be using the original input values for self.day
and self.month, which could be different from their actual value, since they
often get changed as part of the date calculation process.
At this point in time this is not exactly a program, more a collection of files
and modules that I plan to combine later on. The purpose of this program [in
the future] is to find instances of roman/medieval dates in documents and
convert them into conventional dates.