generalize skipping

- rename pytest_xfail to pytest_skip
- dynamic "skipif" and "xfail" decorators
- move most skipping code to the plugin

also coming with this commit:
- extend mark keyword to accept positional args + docs
- fix a few documentation related issues
- leave version as "trunk" for now

--HG--
branch : trunk

testing/path/test_local.py

@@ -208,7 +208,7 @@ class TestLocalPath(common.CommonFSTests):
         assert l[2] == p3
 
 class TestExecutionOnWindows:
-    disabled = py.std.sys.platform != 'win32'
+    skipif = "sys.platform != 'win32'"
 
     def test_sysfind(self):
         x = py.path.local.sysfind('cmd')
@@ -216,7 +216,7 @@ class TestExecutionOnWindows:
         assert py.path.local.sysfind('jaksdkasldqwe') is None
 
 class TestExecution:
-    disabled = py.std.sys.platform == 'win32'
+    skipif = "sys.platform == 'win32'"
 
     def test_sysfind(self):
         x = py.path.local.sysfind('test')
@@ -346,8 +346,7 @@ def test_homedir():
     assert homedir.check(dir=1)
 
 class TestWINLocalPath:
-    #root = local(TestLocalPath.root)
-    disabled = py.std.sys.platform != 'win32'
+    skipif = "sys.platform != 'win32'"
 
     def test_owner_group_not_implemented(self):
         py.test.raises(NotImplementedError, "path1.stat().owner")
@@ -396,7 +395,7 @@ class TestWINLocalPath:
             old.chdir()    
 
 class TestPOSIXLocalPath:
-    disabled = py.std.sys.platform == 'win32'
+    skipif = "sys.platform == 'win32'"
 
     def test_samefile(self, tmpdir):
         assert tmpdir.samefile(tmpdir)

testing/path/test_svnurl.py

@@ -50,12 +50,11 @@ class TestSvnURLCommandPath(CommonSvnTests):
     def test_svnurl_characters_tilde_end(self, path1):
         py.path.svnurl("http://host.com/some/file~")
 
+    @py.test.mark.xfail("sys.platform == 'win32'")
     def test_svnurl_characters_colon_path(self, path1):
-        if py.std.sys.platform == 'win32':
-            # colons are allowed on win32, because they're part of the drive
-            # part of an absolute path... however, they shouldn't be allowed in
-            # other parts, I think
-            py.test.skip('XXX fixme win32')
+        # colons are allowed on win32, because they're part of the drive
+        # part of an absolute path... however, they shouldn't be allowed in
+        # other parts, I think
         py.test.raises(ValueError, 'py.path.svnurl("http://host.com/foo:bar")')
 
     def test_export(self, path1, tmpdir):