Merge pull request #1 from rcharrison/cent65

Support for GCC 4.4.x (CentOS 6.5) - Replaced std::to_string(uint32_t&) with sstreams method.
Changed items to support CentOS 6.5 builds.

* Changed version to 0.8.0-pre5
* Changed cmake requirements from 2.8 to 2.6
* Updated BUILD.md to include build steps for CentOS 6.5 and CentOS 7.  RHEL can use the same.
Merge remote branch 'upstream/master'
IPv4 l3vpn support, possible refactor.