Add custom template tests and fix some bugs

There 2 issues have been addressed:

- If the given g:pydocstring_templates_dir is not ended with a slash
'/', auto append it.

- Reduce the need for one local variable (s:tmpldir) since we always
have to use one variable to store template dir.

autoload/pydocstring.vim

@@ -11,11 +11,10 @@ let s:save_cpo = &cpo
 set cpo&vim
 
 " Path to docstring template.
-if exists('g:pydocstring_templates_dir')
-  let s:tmpldir = g:pydocstring_templates_dir
-else
-  let s:tmpldir = expand('<sfile>:p:h:h') . '/template/pydocstring/'
+if !exists('g:pydocstring_templates_dir')
+  let g:pydocstring_templates_dir = expand('<sfile>:p:h:h') . '/template/pydocstring/'
 endif
+
 " Use comment.txt when cursor is not on def|class keyword.
 if !exists('g:pydocstring_enable_comment')
   let g:pydocstring_enable_comment = 1
@@ -31,7 +30,13 @@ let s:regexs = {
 \ }
 
 function! s:readtmpl(type)
-  let path = expand(s:tmpldir . a:type . '.txt')
+  let tmpldir = g:pydocstring_templates_dir
+  " Append the back slash if needed.
+  if g:pydocstring_templates_dir !~ '/$'
+    let tmpldir =  tmpldir . '/'
+  endif
+
+  let path = expand(tmpldir . a:type . '.txt')
   if !filereadable(path)
     throw 'Template ' . path . ' is not exists.'
   endif

test/custom-template.vader

@@ -1,5 +1,56 @@
-Do (Test 2):
-  iThis is the second test file.
+# vim:set et sw=4 ts=4 tw=79:
+Execute (Setup template dir):
+    Save g:pydocstring_templates_dir
+    let g:pydocstring_templates_dir = './test-template/'
 
-Expect (Test 2):
-  This is the second test file.
+Given python (def foo):
+    def foo():
+        pass
+
+Execute:
+    Pydocstring
+
+
+Expect python:
+    def foo():
+        """foo is """
+        pass
+
+
+Given python (def foo with 1 params):
+    def foo(arg1):
+        pass
+
+Execute:
+    Pydocstring
+
+Expect python:
+    def foo(arg1):
+        """foo
+
+        arg1:
+            arg1 is
+        """
+        pass
+
+
+Given python (def foo with 2 params):
+    def foo(arg1, arg2):
+        pass
+
+Execute:
+    Pydocstring
+
+Expect python:
+    def foo(arg1, arg2):
+        """foo
+
+        arg1:
+            arg1 is
+        arg2:
+            arg2 is
+        """
+        pass
+
+Execute (Clear pydocstring_templates_dir):
+    Restore