Add fork of brace-style rule to support one line arrow functions

[jimjenkins5]

The base brace-style rule in eslint does not have an option to support
one line arrow functions like:

myFunction((b) => { doSomething(b); });

The only option available is allowSingleLine, which would allow the
above code to pass, but would also allow one line if statements.

This commit forks the brace-style rule and adds the option
allowSingleLineArrowFunctions.

[coveralls]

Coverage decreased (-0.4%) to 81.639% when pulling 696a63a on jimjenkins5:allow_oneline_arrow into fdb4381 on silvermine:master.

[coveralls]

Coverage decreased (-0.4%) to 81.639% when pulling 696a63a on jimjenkins5:allow_oneline_arrow into fdb4381 on silvermine:master.

[coveralls]

Coverage decreased (-0.4%) to 81.639% when pulling 696a63a on jimjenkins5:allow_oneline_arrow into fdb4381 on silvermine:master.

[coveralls]

Coverage decreased (-0.4%) to 81.639% when pulling 696a63a on jimjenkins5:allow_oneline_arrow into fdb4381 on silvermine:master.

[coveralls]

Coverage decreased (-0.4%) to 81.639% when pulling c631354 on jimjenkins5:allow_oneline_arrow into fdb4381 on silvermine:master.

[jthomerson]

Just did a quick glance. I'll leave it to @yokuze to do the more thorough review.

[jthomerson]

Need to add a header like https://github.com/silvermine/eslint-plugin-silvermine/blob/696a63ae15932a45fbd0562f10eef0842f309aba/lib/rules/indent.js

[yokuze]

Your comment and commit message says the name of the option is allowSingleLineArrowFunctions but the code has allowSingleLineArrow. I think allowSingleLineArrowFunctions is clearer.

Everything else looks good.

[jimjenkins5]

Actually, I changed it to allowSingleLineArrow to make it more consistent with other eslint rules. For example: https://eslint.org/docs/rules/space-before-function-paren#options asyncArrow not asyncArrowFunction. This is just one example, but ESLint doesn't seem to add Function in their rules and options. I'll update the commit message.

[yokuze]

Looks fine.