Docstring grammar typos and changes (bbatsov#186)

This fixes two typos within the docstring grammar block and an error in conventional usage of the word ‘comprise’. It also arguably improves the flow of this section.

Author: yakryder

README.adoc

@@ -1982,22 +1982,21 @@ can identify them.
 
 === Docstring Grammar [[docstring-grammar]]
 
-Docstrings should be comprised from
-proper English sentences - this means every sentences should start
-with an capitalized word and should end with the proper punctuation. Sentences
-should be separated with a single space.
+Docstrings should be composed of well-formed English sentences. Every sentence 
+should start with a capitalized word, be gramatically coherent, and end 
+with appropriate punctuation. Sentences should be separated with a single space.
 
 [source,clojure]
 ----
 ;; good
 (def foo
  "All sentences should end with a period (or maybe an exclamation mark).
- And the period should be followed by a space, unless it's the last sentence.")
+ The sentence should be followed by a space, unless it concludes the docstring.")
 
 ;; bad
 (def foo
  "all sentences should end with a period (or maybe an exclamation mark).
- And the period should be followed by a space, unless it's the last sentence")
+ The sentence should be followed by a space, unless it concludes the docstring.")
 ----
 
 === Docstring Indentation [[docstring-indentation]]