massive aggregator improvements.

aggregators

• massive aggregation improvements. they now run faster (sometimes by 20x), use less memory and can handle much more load. see #227 , #230
• add derive (rate) aggregator #230
• aggregator regex cache, which lowers cpu usage and increases the max workload, in exchange for a bit more ram usage. #227 By default, the cache is enabled for aggregators set up via commands (init commands in the config) but disabled for aggregators configured via config sections (due to a limitation in our config library)

docs

• add dashboard explanation screenshot #208

packaging and versioning

• fix logging on cent6/amzn/el6 #224 43b265d
• Fix the creation of /var/run/carbon-relay-ng directory #213
• version argument to get the version

other

• disable http2.0 support for grafanaNet route, since an incompatibility with nginx was resulting in bogus 400 Bad Request responses. note this fix does not properly work, use 0.9.3-1 instead.
• track allocated memory