Updated `README.md': reflect current module status
New `module/mongo': mongodb site module
New `module/softlayer'

New site module that interfaces with `extern/softlayer'.
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.
Updated `unit/travis': force pseudo-random device