Add HADOOP_VERSION variable, and bump to 3.1.2 to try to fix download…

… failure

(cherry picked from commit 56ec1b7)

Update HISTORY.md and doc links for 1.6.0.

Update version numbers to 1.5.1

Update HISTORY.md and example links for 1.5.0 release.

Bump version to 1.4.2

Bump version numbers to 1.4.1

Merge pull request TileDB-Inc#1026 from TileDB-Inc/ttd/update-go-doc-…

…link

Update Go documentation link to use v0.2.0 tag.

Update HISTORY.md for 1.3.2 release notes

update HISTORY.md

small fix to compile on gcc 4.8.2

PR TileDB-Inc#827

(cherry picked from commit 31b66d2)