Adding gzipped-XML-tree support to gmond, gmetad, and gmetad-python

This patch does the following:
- Adds a command-line parameter for gmond, "-z", which causes it to
  emit its output XML trees as a gzip stream instead of as plaintext
- Changes gmetad and gmetad-python to automatically detect a
  gzipped data stream from a gmond and handle it appropriately
Attempt to fix travis build.
Support for PPA with libmemcached-1.0 backports for memcached support.
Merge pull request #80 from comptonqc/patches_gzip

Adding gzipped-XML-tree support to gmond, gmetad, and gmetad-python
Add zlib support for new compression dependency.
Update gmond/modules/python/mod_python.c

Upped metric name limits to the maximum that common FS's (such as extFS) wil allow.
Merge pull request #81 from skemper/patch-1

Update gmond/modules/python/mod_python.c
ignore shutdown errors
add delete metrics
add decr and incr metrics
Merge pull request #82 from graphaelli/master

Memcached python module updates
Use strtoull when available to parse network metrics on Linux
Merge pull request #83 from trevorr/bug342

Use strtoull when available to parse network metrics on Linux
libmetics/linux/metrics: skip vlan interfaces when getting network stats. VLAN traffic is accounted in master interfaces.
Merge pull request #84 from lflis/master

libmetrics/linux fix: skip vlan interfaces when collecting network stats
Adjust behavior to work properly with non-existent graphite prefixes (should fix #87, fix #86)