Remove sampling from libcontainer CPU stats.

Sampling should be done by higher layer in configurable intervals. This
change removes the percentage stat as sampling is required for this.

Docker-DCO-1.1-Signed-off-by: Victor Marmol <vmarmol@google.com> (github: vmarmol)
Merge pull request #174 from vmarmol/no-sleep

Remove sampling from libcontainer CPU stats.
Remove erroneous reference to `path` in description and error list;
add format description for `id` string;
add "invalid format" error for `id` string;
remove initial capitals on references to parameter names;
remove reference to `initialConfig`;
add description of id checking.

Signed-off-by: Steve Powell <spowell@pivotal.io>
Merge pull request #172 from cf-guardian/create-api

Correct Create() api call description in Factory interface.