pep8 fixes + license
Added apache 2.0 license
Fixes #8
Add heap-used-percent metric
add thread pool stats
remove pre 1.0 stats
Revert "remove pre 1.0 stats"

This reverts commit 5aa197f452a1ff0e5bf60c5a5f0845b18d9fd8fc.
use ES1 stats for versions >=1.0