Fixed fade_in.m and moved it to "Helper" folder

Made it so that it now accepts instances of time where: t < 1 or t is not a whole number.
Also moved it to the 'Helper' folder

src/NotWorking/fade_in.m

@@ -1,43 +0,0 @@
-function output = fade_in(input, time)
-    % Creates a fade-in sound effect that lasts a given
-    % time parameter of the input sound signal
-    % By Yalu Ouyang
-    
-
-    % input: a 1D array that represents the sound signal in the time domain
-    % time: how long the fade in effect should last
-    % Shouldn't be longer than the input signal (in which case the function
-    % treats it as the duration of the signal)
-    % Returns modified signal in the time domain (output).
-    
-    len = length(input);
-    
-    % need to use whole number for time
-    time = round(time);
-    
-    % if time parameter longer than signal, treat time as
-    % the duration of original signal
-    if time > len
-        time = len;
-    end
-    
-    % in order to create array, time >=1
-    % if not, it's arbitrarily set to 1
-    % in which case the fade_in effect
-    % is virtually nonexistent
-    if time < 1
-        time = 1;
-    end
-
-    % set multiplier as 1D array
-    % fade in effect: from no volume to full volume of signal
-    multiplier = (1 : time) / time;
-    
-    while length(multiplier) < len
-        multiplier = [multiplier 1];
-    end
-    % the resulting fade-in output  
-    output = input .* multiplier;
-end
-
-% This is useful for making videos, specifically the intro part