Rephrase introduction per @mikegee's review

Author: rlue

README.md

@@ -4,8 +4,9 @@
 as a drop-in alternative to its default testing framework, Minitest.
 
 In RSpec, tests are not just scripts that verify your application code.
-They’re also detailed explanations of how the application is supposed to behave,
-expressed in plain English, or in other words, _specs._
+They’re also specifications (or _specs,_ for short):
+detailed explanations of how the application is supposed to behave,
+expressed in plain English.
 
 Use **[`rspec-rails` 1.x][]** for Rails 2.x.