Add reconstruction circle option to transform.radon.
Tests for reconstruction circle option for transform.radon.
Add reconstruction circle option to transform.iradon.
Tests for reconstruction circle mode in transform.iradon.
Correct documentation and string formatting.
PEP8 style changes for transform.radon_transform and its tests
Style improvements in docstrings in transform.radon_transform
Update contributors
Merge pull request #567 from josteinbf/radon-reconstruction-circle

ENH: Option to use a reconstruction circle in transform.radon/iradon.