Respect PEP 440 (#1777)

* Respect PEP 440

Change unreleased version numbers as to respect PEP 440.  Rather than
`0.10.0-9-g89a1a98` we will have `0.10.0+dev9.g89a1a98`.  This means
automated setuptools requirements can be respected.  Closes #1300.

* The fallback version string should also respect PEP 440

Author: gerritholl

setup.py

@@ -105,11 +105,14 @@
             # partial clone, manually construct version string
             # this is the format before we started using git-describe
             # to get an ordering on dev version strings.
-            rev = "v%s.dev-%s" % (VERSION, rev)
+            rev = "v%s+dev.%s" % (VERSION, rev)
 
         # Strip leading v from tags format "vx.y.z" to get th version string
         FULLVERSION = rev.lstrip('v')
 
+        # make sure we respect PEP 440
+        FULLVERSION = FULLVERSION.replace("-", "+dev", 1).replace("-", ".")
+
 else:
     FULLVERSION += QUALIFIER