idiom/functional-options: fix formatting and naming

Author: tmrts

README.md

@@ -104,7 +104,7 @@ __Idioms__:
 
 | Pattern | Description |
 |:-------:| ----------- |
-| [Functional Options](idiom/functional_options.md) | Allows creating clean APIs with sane defaults and idiomatic overrides |
+| [Functional Options](idiom/functional-options.md) | Allows creating clean APIs with sane defaults and idiomatic overrides |
 
 __Anti-Patterns__:
 

idiom/functional_options.md renamed to idiom/functional-options.md

@@ -1,10 +1,12 @@
 # Functional Options
+
 Functional options are a method of implementing clean/eloquent APIs in Go.
 Options implemented as a function set the state of that option.
 
 ## Implementation
 
 ### Options
+
 ```go
 package file
 
@@ -44,6 +46,7 @@ func Permissions(perms os.FileMode) Option {
 ```
 
 ### Constructor
+
 ```go
 package file
 
@@ -77,6 +80,7 @@ func New(filepath string, setters ...Option) error {
 ```
 
 ## Usage
+
 ```go
 emptyFile, err := file.New("/tmp/empty.txt")
 if err != nil {