Feature/triangle component

Added more features to trianglepath component. 
It can have a rounded vertex with each vertex having a different radius. An upper limit has been imposed on the radius though which is the inradius of the triangle.

For calculating the inradius, the formula 
r (inradius) = Area of triangle/semiperimeter of triangle 
has been used.

The area has been calculating using Heron's formula. The method for calculating the semiperimeter has been added as well.
@shamasis So, do you want the constructor to have a flexibility that if there are 7 arguments, last one should be considered as the radius for each vertex.
Correct me if I am wrong.