Modifications to random walker segmentation algorithm:

* returning the probability to belong to a label instead of only the most
  likely label is now possible

* fixing some type issues

* handling non-consecutive label values
Add morphological reconstruction with test and example.
improve and restructure geomtric transformations
remove old import
add example to make_tform doc string
update contributors
fixe index errors and improve setup of some matrices
apply PEP8 guideline
remove inconsistent numeric correction and fix test case
change API design and rename some functions
change arguments of function estimate_transformation
fix wrong exception type
fix doc string formatting of function estimate_transformation
redesign class interface
fix inconsistent doc strings
fix transformation union and add test case
change interface of transformation merging
add support for using transformation objects in warp function
extend doc string example for geometric transformations
add missing doc string for polynomial forward transformation