Add test to provide sanity check for Prmd#render
Add test to provide sanity check for Prmd#render

Use the core parts of test/commands/verify_test.rb to define a basic
sanity checking test for Prmd#render. For now, the test essentially
verifies that Prmd#render successfully produced some Markdown. This will
at least let us know that it didn't throw an exception. Over time, this
test can grow to assert more specific results of Prmd#render.

michaelsauter/prmd,mlr/prmd,junya-i/prmd,michaelsauter/prmd,ruprict/prmd,uberjay/prmd,shopkeep/prmd,niaeashes/prmd,ruprict/prmd,niaeashes/prmd,hmac/prmd,IceDragon200/prmd,mlr/prmd,MobileDevHQ/prmd,interagent/prmd,araines/prmd,junya-i/prmd,hx/prmd,robhurring/prmd,araines/prmd,hx/prmd,shopkeep/prmd,interagent/prmd,uberjay/prmd,IceDragon200/prmd,MobileDevHQ/prmd,hmac/prmd,robhurring/prmd