Added missing word and link

Based on the keypoints found we have to +extract+ features (linked tutorial which explains how features work in pcl)
Tutorial (and some small fixes) for the prerejective pose estimation routine (#129)
Merge pull request #161 from andersgb1/master

Tutorial (and some small fixes) for the prerejective pose estimation routine (#129)
Fix: iren is the the right interactor where to set picker
Changed hog class with a new optimized version which exploits SSE2 operations (3x speedup in descriptor computation).
Fixed bug multiple definitions of hog (moved hog.hpp to hog.cpp).
Bug fixed in hog.g: clip_ variable changed from bool to float.
Remove unused variable
Added non-SSE version of the hog code.
Removed some compilation warnings from people module.
Merge remote-tracking branch 'mmunaro/master'

Conflicts:
	people/include/pcl/people/impl/hog.hpp
	people/include/pcl/people/impl/person_classifier.hpp
Bring back clang in Travis CI

- Add working Boost 1.53 PPA
- Use default CFLAGS
spelling mistake. Classname Clipper3D is case-sensitive in MSVC2010.
Don't use optimized build flags for Travis
Kinfu 30% performance drop bugfix. In the modified CUDA files references to functions Block::reduce with an argument plus() were removed and a new reduce function was added instead.
Dual quaternion transformation estimation algorithm added
Removed dead code in esf.hpp with potential memory access violations
Merge pull request #168 from szagoruyko/kinfufix

Kinfu 30% performance drop bugfix
Merge pull request #170 from jakobkirkegaard/master

Removed dead code in esf.hpp for fixing issue #87
Namespace, prefix, and lowercase sse functions

This fixes a compile error on OS X where the
MIN function collided with a MIN macro.

The fix namespaces the functions in pcl::common,
prefixes the functions with `sse_`, and lowercases
them to prevent interefence from macros.