Update document-store to document store (#255)

README.md

@@ -939,7 +939,7 @@ Benchmarking and profiling might point you to the following optimizations.
 
 ### NoSQL
 
-NoSQL is a collection of data items represented in a **key-value store**, **document-store**, **wide column store**, or a **graph database**.  Data is denormalized, and joins are generally done in the application code.  Most NoSQL stores lack true ACID transactions and favor [eventual consistency](#eventual-consistency).
+NoSQL is a collection of data items represented in a **key-value store**, **document store**, **wide column store**, or a **graph database**.  Data is denormalized, and joins are generally done in the application code.  Most NoSQL stores lack true ACID transactions and favor [eventual consistency](#eventual-consistency).
 
 **BASE** is often used to describe the properties of NoSQL databases.  In comparison with the [CAP Theorem](#cap-theorem), BASE chooses availability over consistency.
 
@@ -947,7 +947,7 @@ NoSQL is a collection of data items represented in a **key-value store**, **docu
 * **Soft state** - the state of the system may change over time, even without input.
 * **Eventual consistency** - the system will become consistent over a period of time, given that the system doesn't receive input during that period.
 
-In addition to choosing between [SQL or NoSQL](#sql-or-nosql), it is helpful to understand which type of NoSQL database best fits your use case(s).  We'll review **key-value stores**, **document-stores**, **wide column stores**, and **graph databases** in the next section.
+In addition to choosing between [SQL or NoSQL](#sql-or-nosql), it is helpful to understand which type of NoSQL database best fits your use case(s).  We'll review **key-value stores**, **document stores**, **wide column stores**, and **graph databases** in the next section.
 
 #### Key-value store