Asset range option

While writing tests, I encountered a problem with the number of vests changing over time. I've created a function that works similarly to python's built-in range() function. It works like this:

tt.Asset.Range(tt.Asset.Test(1), tt.Asset.Test(2))

use analogous to:

range(1, 2)

This allowed me to achieve my goal:

assert tt.Asset.Test(2) in tt.Asset.Range(tt.Asset.Test(1), tt.Asset.Test(3))

I also added the option of specifying the upper deviation percentage:

tt.Asset.Range(tt.Asset.Test(1), percentage_range=10) 

the above case should be understood as follows: from tt.Asset.Test(1) to tt.Asset.Test(1) + 10%

@mzebrak, @kmochocki