Major improvements to precision and aesthetics

CHANGES

- Added precision with rounding, square roots, etc. Not seen throughout
the entire program, but it will be very soon.

- More precise comparisons using ‘modf’

- Added error handlers to catch signals other than ‘ctrl-c’

- MIT License added

- ‘clear’ is now ‘clear_term(POSIX)’ for lack of confusion

- Using STD namespace

- Overall improvements to the program, the precision, and the
aesthetics.

BUGS

- Certain integer variables that are the numerator are set equal to -b
plus/minus the square root of the discriminant. This causes loss of
precision when the discriminant is not a perfect square (e.g. sqrt[27]
would become 5). Rather than changing the variable types from integer
to double, I plan on simplifying the square root of the discriminant
into simplest radical form as done in the solutions to non-real roots.
This will most likely be put into its own function for easy use
throughout the program and for ensured precision.

- Simplifying has not been added to all parts of the program. It has,
however, been added to many parts and will be seen throughout the
program very soon.

- The user input has to be an integer value. I will be changing this to
float or double so decimal coefficients are supported. When I changed
a, b, and c to doubles, the program started acting strange. I will
smooth out the issues with that and change the program very soon. I
also tried inserting a conditional to catch unsupported user input but
the program still acted strangely.