default metric_type to GAUGE

While setting up Librato, I noticed that multiple collectors are not
setting the metric_type parameter (important ones, such as cpu and
network), and thus getting the default of COUNTER. They then getting
recorded wrong and show up as a flat graph. I think COUNTER is the
wrong default, as most metrics collected by Diamond are actually of
GAUGE type. It is also much easier to tell when a counter is accidently
being reported as a guage than when a gauge is being reported as a
counter.
convert to float/int
Fix broken shortened URL
Use str_to_bool to interpret 'use_sudo' in collectors
PEP8 and Doc updates
Merge pull request #338 from wadey/default-metric-type

default metric_type to GAUGE
Merge pull request #339 from bclermont/memcached-type

Fix MemcachedCollector
Merge pull request #343 from jreitz/master

Fix 'use_sudo' config parsing in collectors
Merge pull request #341 from bitprophet/patch-1

Fix broken shortened URL
Per #341, this shortens the url down to fit in the 80 character limit.
Doc updates
Overriding flush function to publish metrics for every collector
Fixed the postgres collector so that if no database is specified it's not passed to psycopg2. This allows it to establish a non-db connection properly over TCP as opposed to erroring out
add new option "simple" for LoadAverageCollector to enable simple output
Doc updates indicating which files are auto-generated
Merge pull request #347 from kostecky/postgres_collector_connect_fix

Fixed the postgres collector so that if no database is specified it's no...
Merge pull request #346 from nitinka/http_post_handler

Overriding flush function to publish metrics for every collector
Merge pull request #348 from huoxy/master

Add new option to enable 'simple' output for LoadAverageCollector.
Merge branch 'master' of github.com:BrightcoveOS/Diamond
Use str_to_bool rather then hard coded strings for simple bool