Forbid build metadata ordering (See #18)

SemVer 2.0.0 states that "Build metadata SHOULD be ignored when
determining version precedence".

This means that, when comparing ``0.1.0+1`` to ``0.1.0+bcd``::

    >>> Version('0.1.0+1') == Version('0.1.0+bcd')
    False
    >>> Version('0.1.0+1') != Version('0.1.0+bcd')
    True
    >>> Version('0.1.0+1') < Version('0.1.0+bcd')
    False
    >>> Version('0.1.0+1') > Version('0.1.0+bcd')
    False
    >>> Version('0.1.0+1') <= Version('0.1.0+bcd')
    False
    >>> Version('0.1.0+1') >= Version('0.1.0+bcd')
    False
    >>> compare(Version('0.1.0+1'), Version('0.1.0+bcd'))
    NotImplemented

This change also has the following effects:
- When including build metadata in a ``Spec``, the only valid options
  are ``Spec('==0.1.0+sth')`` and ``Spec('!=0.1.0+sth')``
- The meaning of ``Spec('==0.1.0+')`` is now "Only version 0.1.0 without
  build metadata"
- ``Spec('==0.1.0')`` now matches ``Version('0.1.0+anything')``

1 files changed, 0 insertions, 7 deletions

diff --git a/tests/test_spec.py b/tests/test_spec.py
index 7a645f9..a13cb0b 100644
--- a/tests/test_spec.py
+++ b/tests/test_spec.py
@@ -154,10 +154,3 @@ class FormatTests(unittest.TestCase):
         self.assertLess(Version('1.0.0-beta.2'), Version('1.0.0-beta.11'))
         self.assertLess(Version('1.0.0-beta.11'), Version('1.0.0-rc.1'))
         self.assertLess(Version('1.0.0-rc.1'), Version('1.0.0'))
-
-
-
-class PrecedenceTestCase(unittest.TestCase):
-    pass
-
-