DOC: Fix links and small typo in README (#53)
DOC: Fix links and small typo in README (#53)

Links were pointing to `TubeTK/(include|src|src/Applications)` but
there is no `TubeTK` folder, so it's removed.
aylward/ITKTubeTK,thewtex/TubeTK,thewtex/TubeTK,aylward/ITKTubeTK,thewtex/TubeTK,aylward/ITKTubeTK,aylward/ITKTubeTK,thewtex/TubeTK