Remove 'aliases' property

Allow setting several names using 'name' property instead, e.g.
':name "-f --foo"' instead of ':aliases {"-f", "--foo"}'.

This change breaks documented interface of 0.3.x.

spec/help_spec.lua

@@ -146,7 +146,7 @@ Options:
 
    it("creates correct help message for commands", function()
       local parser = Parser "foo"
-      parser:flag "-q" "--quiet"
+      parser:flag "-q --quiet"
       local run = parser:command "run"
          :description "Run! "
       run:option "--where"

spec/pparse_spec.lua

@@ -4,7 +4,7 @@ getmetatable(Parser()).error = function(_, msg) error(msg) end
 describe("tests related to :pparse()", function()
    it("returns true and result on success", function()
       local parser = Parser()
-      parser:option "-s" "--server"
+      parser:option "-s --server"
       local ok, args = parser:pparse{"--server", "foo"}
       assert.is_true(ok)
       assert.same({server = "foo"}, args)
@@ -20,8 +20,8 @@ describe("tests related to :pparse()", function()
 
    it("still raises an error if it is caused by misconfiguration", function()
       local parser = Parser()
-      parser:option "--foo"
-         :aliases {1, 2, 3}
-      assert.has_error(function() parser:pparse{} end)
+      parser:flag "--foo"
+         :action(error)
+      assert.has_error(function() parser:pparse{"--foo"} end)
    end)
 end)

src/argparse.lua

@@ -98,19 +98,16 @@ local function typechecked(name, ...)
    return {name, function(_, value) typecheck(name, types, value) end}
 end
 
-local aliased_name = {"name", function(self, value)
+local multiname = {"name", function(self, value)
    typecheck("name", {"string"}, value)
-   table.insert(self._aliases, value)
-   -- Do not set _name to value if there is a name already.
-   return self._name
-end}
 
-local aliased_aliases = {"aliases", function(self, value)
-   typecheck("aliases", {"table"}, value)
-
-   if not self._name then
-      self._name = value[1]
+   for alias in value:gmatch("%S+") do
+      self._name = self._name or alias
+      table.insert(self._aliases, alias)
    end
+
+   -- Do not set _name as with other properties.
+   return true
 end}
 
 local function parse_boundaries(str)
@@ -200,8 +197,7 @@ local Parser = new_class({
 local Command = new_class({
    _aliases = {}
 }, {
-   aliased_name,
-   aliased_aliases,
+   multiname,
    typechecked("description", "string"),
    typechecked("epilog", "string"),
    typechecked("target", "string"),
@@ -236,8 +232,7 @@ local Option = new_class({
    _mincount = 0,
    _overwrite = true
 }, {
-   aliased_name,
-   aliased_aliases,
+   multiname,
    typechecked("description", "string"),
    typechecked("target", "string"),
    boundaries("args"),