Initialize rubocop variables in one place

autoload/ale/fixers/rubocop.vim

@@ -1,19 +1,5 @@
-" Set this option to change Rubocop options.
-if !exists('g:ale_ruby_rubocop_options')
-    " let g:ale_ruby_rubocop_options = '--lint'
-    let g:ale_ruby_rubocop_options = ''
-endif
-
-if !exists('g:ale_ruby_rubocop_executable')
-    let g:ale_ruby_rubocop_executable = 'rubocop'
-endif
-
-function! ale#fixers#rubocop#GetExecutable(buffer) abort
-    return ale#Var(a:buffer, 'ruby_rubocop_executable')
-endfunction
-
 function! ale#fixers#rubocop#GetCommand(buffer) abort
-    let l:executable = ale#Var(a:buffer, 'ruby_rubocop_executable')
+    let l:executable = ale#handlers#rubocop#GetExecutable(a:buffer)
     let l:exec_args = l:executable =~? 'bundle$'
     \   ? ' exec rubocop'
     \   : ''

autoload/ale/handlers/rubocop.vim

@@ -0,0 +1,6 @@
+call ale#Set('ruby_rubocop_options', '')
+call ale#Set('ruby_rubocop_executable', 'rubocop')
+
+function! ale#handlers#rubocop#GetExecutable(buffer) abort
+    return ale#Var(a:buffer, 'ruby_rubocop_executable')
+endfunction