'**SUMMARY**
This is the angle of the line, from the leftmost point to the rightmost point
Returns angle (theta) in radians, with 0 = horizontal, -pi/2 = vertical positive slope, pi/2 = vertical negative slope
**RETURNS**
An angle value in degrees.
**EXAMPLE**
>>> img = Image("OWS.jpg")
>>> ls = img.findLines
>>> for l in ls:
>>>    if l.angle() == 0:
>>>       print "I AM HORIZONTAL."'

def angle(self):

    a = 0
    b = 1
    if (self.end_points[a][0] > self.end_points[b][0]):
        b = 0
        a = 1
    d_x = (self.end_points[b][0] - self.end_points[a][0])
    d_y = (self.end_points[b][1] - self.end_points[a][1])
    return float((360.0 * (atan2(d_y, d_x) / (2 * np.pi))))
