Merge branch 'release/1.1.0' into develop

* release/1.1.0:
  Release 1.1.0
Fix uninitialized value

We decide whether to close an existing file based on this field, so we'd
better make sure to initialize it.
Merge branch 'feature/uninitialized' into develop

* feature/uninitialized:
  Fix uninitialized value
Final snapshot in periodic background thread

The periodic manager's background thread will now always fire its
callback one final time when the thread is canceled.  For the file
rotator, this means that the last file will have a final entry
containing the values of the statistics when the background thread was
canceled (which is usually at the end of the process).
Merge branch 'feature/periodic-last' into develop

* feature/periodic-last:
  Final snapshot in periodic background thread
Rendering deltas with rates

Given two snapshots, and the interval between them, we can compute the
rate that derive counters are increasing by.  This patch adds new
functions for rendering two snapshots that includes rates for any
derives.  (The rate portion is left blank for gauges.)

The periodic interface has also been updated to keep track of the
previous snapshot, along with the current one, to make it easy for
background threads to calculate rates.
Merge branch 'feature/derive-rate' into develop

* feature/derive-rate:
  Rendering deltas with rates
Release 2.0.0
Merge branch 'release/2.0.0'

* release/2.0.0:
  Release 2.0.0
  Rendering deltas with rates
  Final snapshot in periodic background thread
  Fix uninitialized value