Test for valid tags during parse

fixes StackExchange/bosun#221
Pass tag validation errors
Just pass when there is an erroneous CPU spike measurement of os.cpu in win
Monitor the number of ip addresses in Linux
Revert "Just pass when there is an erroneous CPU spike measurement of os.cpu in win"

The windows CPU counter is fraught with peril.

This reverts commit e534c7e44e478bfca7e59e40fd190bee4cac4da9.
Append localhost on queue
Return after error
Collect stats from /proc/net/snmp

This makes up part of the data of netstat statistics `netstat -s` besides /proc/net/netstat (which we already collect)
Remove empty line
Add missing CPU field, change field length check

Fixes #54
Set var for rate type
Get rid of metric variable, get rid of continue
Default send location to http://bosun/

Optionally disable metadata sending. This is work to allow bosun to stop
relaying :4242 traffic.
Don't fatal on bad external tag

fixes #62
More verbose bad tag errors
Return, don't print, scan error
If /sys/class/net/if/speed exists and is readable, use it to populate the linux.net.ifspeed and os.net.ifspeed metric
Monitor basic jvm GC activity on hbase region servers
Don't shadow type var, style
Merge pull request #65 from StackExchange/jmx_gc

Monitor basic jvm GC activity on hbase region servers