Make nginx-push-stream more repeatable

Using the approach from nexedi/slapos!258 I checked that all dependencies was pinned down.

Some eggs where not pinned, all git repositories seems to be pinned ( I found there was only `[nginx-push-stream-module]`)

/reviewed-on nexedi/slapos!269

software/nginx-push-stream/software.cfg

@@ -47,3 +47,16 @@ mode = 0644
 [versions]
 slapos.recipe.template = 4.3
 slapos.toolbox = 0.73
+dnspython = 1.15.0
+PyRSS2Gen = 1.1
+erp5.util = 0.4.50
+passlib = 1.7.1
+GitPython = 2.1.8
+lockfile = 0.12.2
+apache-libcloud = 2.2.1
+feedparser = 5.2.1
+atomize = 0.2.0
+inotifyx = 0.2.2
+gitdb2 = 2.0.3
+pyasn1 = 0.4.2
+smmap2 = 2.0.3