fixed const iterator errors (win64)
Fix degenerated rotation axis bug when normal is parallel to x axis.
Remove the redundant scene_search_tree_.
Use depth camera intrinsics unless RGB image registration is active.
Add graph segmentation using random walks

This is an implementation of the algorithm described in "Random Walks
for Image Segmentation" by Leo Grady which works with BGL graphs.
Add unit tests for random walker segmentation
Add ${EIGEN_VERSION} to FindEigen.cmake
Add guards to check Eigen version

Random walker needs Eigen::Sparse module, which is available since
version 3.1.0.
Add custom PPA to get latest Eigen for Travis
Fix warnings in common/io.hpp

> io.hpp:275:30: warning: comparison of integers of different signs: 'int' and 'size_type' (aka 'unsigned long') [-Wsign-compare]
Fix warnings in octree/octree_container.h

> octree_container.h:166:7: warning: 'pcl::octree::OctreeContainerEmpty::getSize' hides overloaded virtual function [-Woverloaded-virtual]
> octree_container.h:96:7: note: hidden overloaded virtual function 'pcl::octree::OctreeContainerBase::getSize' declared here: different qualifiers (none vs const)
Fix warnings in sample_consensus/sac_model_circle3d.hpp

> sac_model_circle3d.hpp:283:24: warning: comparison of integers of different signs: 'size_t' (aka 'unsigned long') and 'Index' (aka 'long') [-Wsign-compare]
Fix warnings in sample_consensus/sac_model_registration_2d.hpp

> sac_model_registration_2d.hpp:93:21: warning: unused variable 'pt_tgt' [-Wunused-variable]
Fix warnings in filters/filter_indices.h

> filter_indices.h:186:7: warning: 'pcl::FilterIndices<pcl::PointXYZ>::applyFilter' hides overloaded virtual function [-Woverloaded-virtual]
> filter_indices.h:294:7: warning: 'pcl::FilterIndices<pcl::PCLPointCloud2>::applyFilter' hides overloaded virtual function [-Woverloaded-virtual]
Fix warnings in filters/sampling_surface_normal.hpp

> sampling_surface_normal.hpp:52:30: warning: comparison of integers of different signs: 'unsigned int' and 'int' [-Wsign-compare]
> sampling_surface_normal.hpp:128:13: warning: comparison of integers of different signs: 'const int' and 'unsigned int' [-Wsign-compare]
> sampling_surface_normal.hpp:167:34: warning: comparison of integers of different signs: 'unsigned int' and 'const int' [-Wsign-compare]
Fix warnings in filters/median_filter.hpp

> median_filter.hpp:58:21: warning: comparison of integers of different signs: 'int' and 'uint32_t' (aka 'unsigned int') [-Wsign-compare]
> median_filter.hpp:59:23: warning: comparison of integers of different signs: 'int' and 'uint32_t' (aka 'unsigned int') [-Wsign-compare]
> median_filter.hpp:68:45: warning: comparison of integers of different signs: 'int' and 'uint32_t' (aka 'unsigned int') [-Wsign-compare]
> median_filter.hpp:69:45: warning: comparison of integers of different signs: 'int' and 'uint32_t' (aka 'unsigned int') [-Wsign-compare]
Merge pull request #412 from taketwo/fix-warnings

Fix compiler warnings
Merge pull request #396 from hovren/fix-392

Use depth camera intrinsics unless RGB image registration is active.
Updated documentation of point picking event for indexing- issue #266
Fixed tabs to spaces