Merge pull request #721 from rich-murphey/patch-1

Update associated-items.md.  "it"->is

Author: ehuss

src/items/associated-items.md

@@ -18,7 +18,7 @@ Every associated item kind comes in two varieties: definitions that contain the
 actual implementation and declarations that declare signatures for
 definitions.
 
-It is the declarations that make up the contract of traits and what it available
+It is the declarations that make up the contract of traits and what is available
 on generic types.
 
 ## Associated functions and methods
@@ -360,4 +360,4 @@ fn main() {
 [function item]: ../types/function-item.md
 [method call operator]: ../expressions/method-call-expr.md
 [path]: ../paths.md
-[regular function parameters]: functions.md#attributes-on-function-parameters 
+[regular function parameters]: functions.md#attributes-on-function-parameters