Add link to jqplay
Merge pull request #332 from jingweno/master

Add link to jq playground
Add autoconf checks for pthreads; fix #340
Make pthread tls configurable for Mingw build

For the Mingw build we don't want to pull in the pthread DLL just
because we can autodetect pthread support.  That would make the jq.exe
binary not self-contained.
Added unique_by function
Added texts/examples to unique_by function
Merge pull request #360 from slapresta/275-unique-by

unique_by(.foo) function
Merge remote-tracking branch 'upstream/master'