Add hot memory usage to memory graph.

Docker-DCO-1.1-Signed-off-by: Rohit Jnagal <jnagal@google.com> (github: rjnagal)
Merge remote-tracking branch 'upstream/master'

Docker-DCO-1.1-Signed-off-by: Rohit Jnagal <jnagal@google.com> (github: rjnagal)
Merge pull request #195 from rjnagal/master

Add hot memory usage to memory graph.
Merge pull request #190 from rjnagal/bigquery

Initial version of bigquery backend.
Fix bug in influxdb storage driver initialization.
Merge pull request #196 from vishh/influxdb_batch_issue

Fix bug in influxdb storage driver initialization.
Merge pull request #197 from rjnagal/bigquery

Update bigquery README.md for readability and typo fixes
Set 'time' column in InfluxDB driver to preserve precision of stats even while batching writes to the DB.
Merge pull request #201 from vishh/influxdb_batch_issue

Set 'time' column in InfluxDB driver