Add scalastyle linter (#766)

* Add support for scalastyle

* Add scalastyle docs

* scalastyle support for column numbers

* off by one column

* Add tests for scalastyle command and handler

* update readme for scalastyle

* allow full scalastyle options instead of just config file

* fix indentation

* allow scalastyle config file in parent directories by a couple names.

* check for missing match args with empty

* remove echo

* use a for loop

test/command_callback/test_scalastyle_command_callback.vader

@@ -0,0 +1,27 @@
+Before:
+  runtime ale_linters/scala/scalastyle.vim
+
+After:
+  call ale#linter#Reset()
+  let g:ale_scala_scalastyle_options = ''
+  let g:ale_scalastyle_conf_loc = ''
+
+Execute(Should return the correct default command):
+  AssertEqual
+  \   'scalastyle %t',
+  \   ale_linters#scala#scalastyle#GetCommand(bufnr(''))
+
+Execute(Should allow using a custom config file):
+  let g:ale_scalastyle_config_loc = '/dooper/config.xml'
+
+  AssertEqual
+  \   'scalastyle --config ''/dooper/config.xml'' %t',
+  \   ale_linters#scala#scalastyle#GetCommand(bufnr(''))
+
+Execute(Should allow using custom options):
+  let g:ale_scala_scalastyle_options = '--warnings false --quiet true'
+
+  AssertEqual
+  \   'scalastyle --config ''/dooper/config.xml'' --warnings false --quiet true %t',
+  \   ale_linters#scala#scalastyle#GetCommand(bufnr(''))
+

test/handler/test_scalastyle_handler.vader

@@ -0,0 +1,38 @@
+Execute(The scalastyle handler should parse lines correctly):
+  runtime! ale_linters/scala/scalastyle.vim
+
+  AssertEqual
+  \ [
+  \   {
+  \     'lnum': 190,
+  \     'text': 'Missing or badly formed ScalaDoc: Missing @param str',
+  \     'type': 'W',
+  \   },
+  \   {
+  \     'lnum': 200,
+  \     'col': 34,
+  \     'text': 'There should be a space before the plus (+) sign',
+  \     'type': 'E',
+  \   },
+  \   {
+  \     'lnum': 200,
+  \     'col': 1,
+  \     'text': 'There should be a space before the plus (+) sign',
+  \     'type': 'E',
+  \   },
+  \ ],
+  \ ale_linters#scala#scalastyle#Handle(347, [
+  \    'Starting scalastyle',
+  \    'start file /home/test/Doop.scala',
+  \    'warning file=/home/test/Doop.scala message=Missing or badly formed ScalaDoc: Missing @param str line=190',
+  \    'error file=/home/test/Doop.scala message=There should be a space before the plus (+) sign line=200 column=33',
+  \    'error file=/home/test/Doop.scala message=There should be a space before the plus (+) sign line=200 column=0',
+  \    'end file /home/test/Doop.scala',
+  \    'Processed 1 file(s)',
+  \    'Found 0 errors',
+  \    'Found 3 warnings',
+  \    'Finished in 934 ms',
+  \ ])
+
+After:
+  call ale#linter#Reset()