Fix param parsing.

Closes numpy#285

This fixes two tings:

 - When first sentence of the docstring is onteh first line, Parameters
 is not properly parse, which for example mis parsed numpy.array
 docstring.

 - many project have paremeters description list with ` :` afer the
 name, even if no type is present. If there is no space after the `:`
 the parameter name includes the ` :` which is most likely wrong.

numpydoc/docscrape.py

@@ -219,12 +219,14 @@ def _read_sections(self):
                 yield name, self._strip(data[2:])
 
     def _parse_param_list(self, content, single_element_is_type=False):
+        content = dedent_lines(content)
         r = Reader(content)
         params = []
         while not r.eof():
             header = r.read().strip()
-            if ' : ' in header:
-                arg_name, arg_type = header.split(' : ', maxsplit=1)
+            if ' :' in header:
+                arg_name, arg_type = header.split(' :', maxsplit=1)
+                arg_name, arg_type = arg_name.strip(), arg_type.strip()
             else:
                 if single_element_is_type:
                     arg_name, arg_type = '', header

numpydoc/tests/test_docscrape.py

@@ -183,7 +183,12 @@ def test_extended_summary():
     assert doc['Extended Summary'][0].startswith('The multivariate normal')
 
 
-def test_parameters():
+@pytest.mark.parametrize('sig_on_first_line', (True, False))
+def test_parameters(sig_on_first_line):
+    if sig_on_first_line:
+        doc = NumpyDocString(doc_txt.lstrip())
+    else:
+        doc = NumpyDocString(doc_txt)
     assert len(doc['Parameters']) == 4
     names = [n for n, _, _ in doc['Parameters']]
     assert all(a == b for a, b in zip(names, ['mean', 'cov', 'shape']))
@@ -921,6 +926,20 @@ class BadSection:
 def test_empty_first_line():
     assert doc7['Summary'][0].startswith('Doc starts')
 
+doc8 = NumpyDocString("""
+
+        Parameters wit colon and no types:
+
+        Parameters
+        ----------
+
+        data :
+            some stuff, technically invalid
+        """)
+
+
+def test_trailing_colon():
+    assert doc8['Parameters'][0].name == 'data'
 
 def test_no_summary():
     str(SphinxDocString("""