Add: Vagrantfile for easy environment setup

Running and manually testing features of pyperf requires an actual
environment to run in with some third-party services. Likewise,
testing the profilers planned for LXC and ZeroVM will not be possible
except in an environment where these systems are already installed.

Signed-off-by: Kevin Conway <kevinjacobconway@gmail.com>
Fix: Sample code and normalize engine usage

The executor interface was accepting a session while the app_maker
was accepting an engine and building a sessions. Now the executor
accepts and engine instead of a session.

The sample server worked well enough, but it used an in memory
sqlite database. This made it incompatible with running an executor
agent. The database is now a sqlite file in the /tmp/ space.

Signed-off-by: Kevin Conway <kevinjacobconway@gmail.com>
Merge pull request #15 from kevinconway/fix_sample

Fix: Sample code and normalize engine usage
Merge pull request #16 from kevinconway/vagrant

Add: Vagrantfile for easy environment setup