Database Interaction

Created a class called Database Interaction with two methods in it.
addEntry modifies a txt file ("Entries.txt") every time it's called by
adding a line with an input (name) and input (amount), separated by a
comma.  Method sumPersonEntries takes an input (name), then runs through
Entries.txt and adds up all the entries prefixed with the person's name,
then returns the value.

Notes: There's currently no way to delete values.  sumPersonEntries just
takes negative values and subtracts them from sum.