Add SYNOPSIS section for nn_env documentation (fixes #294)
Add SYNOPSIS section for nn_env documentation (fixes #294)

TTimo/nanomsg,wfxiang08/nanomsg,reqshark/nanomsg,potatogim/nanomsg,smithed/nanomsg,smithed/nanomsg,featherweight/ftw-kernel-nanomsg,ttyangf/nanomsg,linearregression/nanomsg,JackDunaway/featherweight-nanomsg,gdamore/mamomsg,modulexcite/nanomsg,pch957/nanomsg,krafczyk/nanomsg,pakozm/nanomsg,reqshark/nanomsg,cosin2008/nanomsg.NET,featherweight/ftw-kernel-nanomsg,pakozm/nanomsg,wfxiang08/nanomsg,wirebirdlabs/featherweight-nanomsg,pch957/nanomsg,JackDunaway/featherweight-nanomsg,gdamore/mamomsg,krafczyk/nanomsg,tempbottle/nanomsg,hyperfact/nanomsg,potatogim/nanomsg,pakozm/nanomsg,ttyangf/nanomsg,TTimo/nanomsg,ttyangf/nanomsg,yan97ao/nanomsg,nirs/nanomsg,tempbottle/nanomsg,imp/nanomsg,gdamore/mamomsg,hyperfact/nanomsg,simplestbest/nanomsg,ttyangf/nanomsg,thisco-de/nanomsg,hyperfact/nanomsg,reqshark/nanomsg,simplestbest/nanomsg,thisco-de/nanomsg,cosin2008/nanomsg.NET,zerotacg/nanomsg,cosin2008/nanomsg.NET,smithed/nanomsg,simplestbest/nanomsg,wfxiang08/nanomsg,modulexcite/nanomsg,TTimo/nanomsg,linearregression/nanomsg,smithed/nanomsg,JackDunaway/featherweight-nanomsg,zerotacg/nanomsg,linearregression/nanomsg,krafczyk/nanomsg,yan97ao/nanomsg,nirs/nanomsg,yan97ao/nanomsg,potatogim/nanomsg,nirs/nanomsg,wirebirdlabs/featherweight-nanomsg,modulexcite/nanomsg,snikulov/nanomsg,imp/nanomsg,imp/nanomsg,tempbottle/nanomsg,TTimo/nanomsg,pch957/nanomsg,wirebirdlabs/featherweight-nanomsg,snikulov/nanomsg,zerotacg/nanomsg