Small code cleanup.
Merged 2 commits from bzr branch.

This commit merges two commits from the previous
bzr branch by Tom Bartol (these were committed to
bzr after the git branch was generated from bzr).

revno 1005:

Preserve mol ID for unimolecular reactions with one product.
e.g.  A -> B

revno 1006:

Add code to preserve molecule id if reaction is a surface reaction with
one product, for example:
a, @surf' -> b' [k]

This commit syncs our new git repo to revno 1008 of the bzr branch.