feat(endecadgraph): new collector

Change-Id: I96d444b13962337f1504f8de961a74b5548f1d6e
Fix rabbitmq test
Support for config merging from specified directory
Update memory.py

Add Committed_AS data to collected keys
new(feat): added collector for chrony time offsets (ntp time skew)

Change-Id: If4863300ed483dcd83280dfe5c6d668eeacad530
Make handling of mongodb config more robust

- Make sure hosts parameter is interpreted correctly
- Enable option to always specify an alias
Improvements to the hadoop collector.

This change implements two major changes necessary to use the hadoop
collector in a production environment. The first change divides the time
by 1000 as the time reported in the metrics files are miliseconds since
epoch. Without this change the following error is thrown from graphite:
struct.error: 'L' format requires 0 <= number <= 4294967295

The second change included here is a truncation step to the file read.
Without a truncation step the metrics file will grow forever, and each
run will re-read the whole metrics file, sending all the old, as well as
the new metrics to the graphite server. By truncating the file after a
successful read we can stop not only the disks from filling up, but we
can also ensure that we never overload the graphite server by re-sending
massive numbers of metrics. This change is optional, and defaulted to
false in order to maintain current semantics.
postgres: make handling queries against pg_stats (etc) for different vers, more flexible
postgres: add pg_stat_database.temp_files/bytes for pg >= 9.2
added a timer to delay influxdb writes

Added a timer to wait for an incremental time in case influxdb is not responding.
This will stop the 100% CPU usage of diamond when influxdb is down.

Instead of calling the _send() each time the batch size is reached (as it will occure for EVERY new metric gathered in case of failure), the function is called only when :
1) the batch size is reached
2) the last _send() request was done X seconds before

X is 2s in normal operation, and is rooted by 2 each time, so first write is after 2s, then 4s, then 8s, 16s and 32s, which is the max.
During this time, the metrics will stay in memory. if more than self.metric_max_cache metrics are stored, stop recording them. 
I did it this way as the array of metrics is multi-level, indexed by its path and we can't easily know how many values are in each path and which one to remove to trim the cache...
This will work AS LONG AS the batch size is less than the cache size, which should always be the case anyway...
changed time_precision from m to ms

influxdb changed the value for the miliseconds time precision from 'm' to 'ms'
gather monit totals memory and cpu metrics if send_totals = True
Add per-collector ability to whitelist/blacklist metrics

- Configured with keys metrics_whitelist and metrics_blacklist
  to the collector's section in the config file
- Keys aren't regexes, straight strings that are comma separated
- Providing both a whitelist and a blacklist will result in an
  exception being thrown
PEP8: Fixes for ELB collector + tests

Now the entire repo passes PEP8!
exim: Allow collector to sudo as any user

Ideally, you would sudo as exim to read the number, not as
root. The defaults are kept as root for backwards compatibility.
Use a regex for metrics_blacklist and whitelist
Add precision to the httpd collector for ReqPerSec BytesPerSec BytesPerReq
Prevent userscript from dying when seeing an invalid line from a script.
Remove unnecessary for loop.
Also collect heap_used_percent - so one can see how close to the limit one is.