Updated `module/net': new, cleanup

New:

    :net:localportping() - for checking if a local tcp port is open or
    not without using a client (but using netstat instead).

    :net:freelocalport() - for finding free local ports to bind to,
    optionally taking a list of preferred ports to check first.

Cleanup:

    General cleanup.
Updated `module/vault': new, clean

The public `read()' function was split up into public and internal.

Unit test for the new private function added.

Cosmetic rearrangement of code.
Updated `libexec/softlayer': flag for cache added

Added a programatic flag (variable) to enable/disable caching, and
set that to false as softlayer API calls are not too costly.
New `module/softlayer'

New site module that interfaces with `extern/softlayer'.
New `module/mongo'
New `module/tunnel'
New `module/pagerduty'
New `module/capistrano'
Updated `travis'

Moved some package installs into the specific module requiring it in
order to reduce the shared build commands, thus speeding up all
builds as a result.
Updated `README.md': reflect current status