Allow user to pass in passing grades

[haydenfree]

CurricularAnalytics.jl/src/Simulation/PassRate.jl

Line 53 in a46afde

passing_grades = ["A", "B", "C", "D", "P"]

Passing grades are currently hardcoded as a string value, but users should be able to pass these in.

Additionally, we should leverage the Grade type defined in DegreeRequirements

CurricularAnalytics.jl/src/DataTypes/DegreeRequirements.jl

Lines 5 to 48 in a46afde

	Grade = UInt64
	# function for converting a letter grade into a integer, divide by 3 to convert to 4-point GPA scale
	function grade(letter_grade::AbstractString)
	if letter_grade == "A➕"
	return convert(Grade, 13)
	elseif letter_grade == "A"
	return convert(Grade, 12)
	elseif letter_grade == "A➖"
	return convert(Grade, 11)
	elseif letter_grade == "B➕"
	return convert(Grade, 10)
	elseif letter_grade == "B"
	return convert(Grade, 9)
	elseif letter_grade == "B➖"
	return convert(Grade, 8)
	elseif letter_grade == "C➕"
	return convert(Grade, 7)
	elseif letter_grade == "C"
	return convert(Grade, 6)
	elseif letter_grade == "C➖"
	return convert(Grade, 5)
	elseif letter_grade == "D➕"
	return convert(Grade, 4)
	elseif letter_grade == "D"
	return convert(Grade, 3)
	elseif letter_grade == "D➖"
	return convert(Grade, 2)
	elseif letter_grade == "P"
	return convert(Grade, 0)
	elseif letter_grade == "F"
	return convert(Grade, 0)
	elseif letter_grade == "I"
	return convert(Grade, 0)
	elseif letter_grade == "WP"
	return convert(Grade, 0)
	elseif letter_grade == "W"
	return convert(Grade, 0)
	elseif letter_grade == "WF"
	return convert(Grade, 0)
	else
	error("letter grade $letter_grade is not supported")
	end
	end

[haydenfree]

This is related to #116