Fix comments on the end of lines.

Fixes #176

spec/syntax/comments_spec.rb

@@ -0,0 +1,17 @@
+# frozen_string_literal: true
+
+require 'spec_helper'
+
+describe 'Comments syntax' do
+  it 'full line comment' do
+    expect(<<~EOF).to include_elixir_syntax('elixirComment', '#\ this\ is\ a\ comment')
+    # this is a comment
+    EOF
+  end
+
+  it 'end line comment' do
+    expect(<<~EOF).to include_elixir_syntax('elixirComment', '#\ this\ is\ a\ comment')
+    IO.puts "some text" # this is a comment
+    EOF
+  end
+end

syntax/elixir.vim

@@ -13,7 +13,7 @@ syn cluster elixirRegexSpecial contains=elixirRegexEscape,elixirRegexCharClass,e
 syn cluster elixirStringContained contains=elixirInterpolation,elixirRegexEscape,elixirRegexCharClass
 syn cluster elixirDeclaration contains=elixirFunctionDeclaration,elixirModuleDeclaration,elixirProtocolDeclaration,elixirImplDeclaration,elixirRecordDeclaration,elixirMacroDeclaration,elixirDelegateDeclaration,elixirOverridableDeclaration,elixirExceptionDeclaration,elixirCallbackDeclaration,elixirStructDeclaration
 
-syn match elixirComment '^\s*#.*' contains=elixirTodo,@Spell
+syn match elixirComment '#.*' contains=elixirTodo,@Spell
 syn keyword elixirTodo FIXME NOTE TODO OPTIMIZE XXX HACK contained
 
 syn keyword elixirKeyword case when with cond for if unless try receive send