Add rule max-attributes-per-line (resolves #47)

docs/rules/max-attributes-per-line.md

@@ -1,33 +1,42 @@
 # Define the number of attributes allows per line (max-attributes-per-line)
 
-Limits the maximum number of props per line to improve readability
+Limits the maximum number of attributes/properties per line to improve readability.
 
 
 ## Rule Details
 
-This rule aims to enforce a number of props per line in templates. It checks all the elements in a template and verifies that the number of props per line does not exceed the defined maximum.
-A prop is considered to be in a new line when there is a line break between two props.
+This rule aims to enforce a number of attributes per line in templates. It checks all the elements in a template and verifies that the number of attributes per line does not exceed the defined maximum.
+An attribute is considered to be in a new line when there is a line break between two attributes.
 
-The default is one prop per line
+There is predefined number of attributes that are acceptable in one-line case, as well as how many attributes are acceptable per line in multi-line case.
+
+The default is one attribute per line for multiline and three attributes per line in singleline.
 
 Examples of **incorrect** code for this rule:
 
 ```js
+<component lorem="1" ipsum="2" dolor="3" sit="4">
+</component>
 
-<component foo="1" bar="3"></component>
-
-<component foo="1" bar="2"
-  foobar="3"></component>
-
+<component
+  lorem="1" ipsum="2"
+  dolor="3"
+  sit="4"
+>
+</component>
 ```
 
 Examples of **correct** code for this rule:
 
 ```js
+<component lorem="1" ipsum="2" dolor="3">
+</component>
 
 <component
-  foo="1"
-  bar="3"
+  lorem="1"
+  ipsum="2"
+  dolor="3"
+  sit="4"
 >
 </component>
 
@@ -38,42 +47,68 @@ Examples of **correct** code for this rule:
 ```
 {
   "vue/max-attributes-per-line": ["error", {
+    "firstline": 1,
     "singleline": 2,
     "multiline": 1
   }]
 }
 ```
+
+### `firstline`
+For muliline declarations, defines if it accepts an attribute in the first line.
+
+The following patterns is considered a warning:
+```js
+// ["error", { "firstline": 1, "singleline": 2, "multiline": 1}]
+<component
+  foo="John" bar="Smith"
+  foobar={5555555}>
+</component>;
+```
+
+The following pattern is not considered a warning:
+```js
+// ["error", { "firstline": 0, "singleline": 3, "multiline": 1}]
+<component
+  foo="John"
+  bar="Smith"
+  foobar={5555555}
+  >
+</component>;
+```
+
+
 ### `singleline`
-Number of maximum number of props when a tag is in a single line.
+Number of maximum attributes per line when the opening tag is in a single line.
 
 The following patterns is considered a warning:
 ```js
-// ["error", { "singleline": 2, "multiline": 1}]
+// ["error", { "firstline": 1, "singleline": 2, "multiline": 1}]
 <component foo="John" bar="Smith" foobar={5555555}></component>;
 ```
 
 The following pattern is not considered a warning:
 ```js
-// ["error", { "singleline": 3, "multiline": 1}]
+// ["error", { "firstline": 1, "singleline": 3, "multiline": 1}]
 <component foo="John" bar="Smith" foobar={5555555}></component>;
 ```
 
 
 ### `multiline`
-Number of maximum number of props when a tag is in a single line.
+Number of maximum attributes per line when a tag is in multiple lines.
 
 
 The following patterns is considered a warning:
 ```js
-// ["error", { "singleline": 2, "multiline": 1}]
+// ["error", { "firstline": 1, "singleline": 2, "multiline": 1}]
 <component foo="John" bar="Smith"
   foobar={5555555}>
 </component>;
 ```
 
 The following pattern is not considered a warning:
 ```js
-// ["error", { "singleline": 3, "multiline": 1}]
+// ["error", { "firstline": 0, "singleline": 3, "multiline": 1}]
 <component
   foo="John"
   bar="Smith"
@@ -84,5 +119,5 @@ The following pattern is not considered a warning:
 
 ## When Not To Use It
 
-If you do not want to check the number of props declared per line you can disable this rule.
+If you do not want to check the number of attributes declared per line you can disable this rule.