Release of v1.3.1

Release of v1.3.0

Changelog:
  * Instructions for `make install` for Linux and Windows (Closes jlblancoc#87).
  * Fix all (?) MSVC conversion warnings (Closes: jlblancoc#95).
  * Avoid need for _USE_MATH_DEFINES in MSVC (Closes: jlblancoc#96)
  * Eigen::Matrix datasets: now uses std::cref() to store a reference to matrix.
  * GSOC2017 contributions by Pranjal Kumar Rai:
    * Support for dynamic datasets.
    * Support for non-Euclidean spaces: SO(2), SO(3)

Fixed: split plane now correctly chooses the dimensions with the larg…

…est span

Fixes jlblancoc#33

fix undefined behavior of knnSearch() if there are less tree nodes th…

…an requested in the search

Release of 1.2.1

Fix storage of const refs.

Previously, the copy operation may lead to unexpected errors or memory
corruption.
Mark this as the release of v1.2.0

Update CHANGELOG.txt

Merge branch 'master' of https://github.com/jlblancoc/nanoflann

Tagging of 1.1.7

tagging of 1.1.6