LMNN implementation based on auxiliary methods hidden in an implementation class.
A few unit tests for LMNN
Merge pull request #1270 from iglesias/feature/lmnn

LMNN implementation and a couple of unit tests
Fixed implicit conversion to NULL warnings
added convert_to_matrix method in SGVector
fixed some crashes in sparse features unit tests
Merge pull request #1271 from gsomix/feature/linereader

SGVector: convert_to_matrix method
fix c++11 compile error
fixed a memory issue related to uninitialised memory which should be NULL
changed sparse matrix parameter registering
Merge pull request #1274 from karlnapf/develop

Fix segfaults in unit tests
Merge pull request #1272 from van51/develop

Fixed travis warnings for implicit conversion from NULL to bool
add CSGObject as supported serialization PT