Updated README with some release schedule information.
Updated README with link to 'merge' ES documentation.
Closes issue #20 - record host environment.

Records cluster info once per benchmark, using data from
"_cluster/nodes", and records cluster stats once per observation using
data from "_cluster/nodes/stats". This will give info on vm, memory use,
gc, etc.

Version bump to 0.0.8
Merge branch 'master' of https://github.com/mkocikowski/esbench