Fix #345 by fixing Url which cannot parse itself when stringified

Closes: #345 (closed)

For more info look into: #345 (comment 188749)

Please take a look: @kmochocki @msobczyk

Basically before it worked like this:

a = Url.parse("-h")  # works
print(a) # "://-h"
b = Url.parse(a)  # works
c = Url.parse(str(a))  # error

but now:

a = Url.parse("-h")  # works
print(a) # "-h"
b = Url.parse(a)  # works
c = Url.parse(str(a))  # works