Fix issue #1083.

This commit escapes the egg "surname" when using git with freeze.
Change "escape" to "translate" in escape_egg_surname().
Update docs to explain the "version" component of the egg name.
Add functional test for issue #1083.
Fix code comment ("tag" to "tag or branch").
DRY up use of repo directory in test_freeze_git_clone().
Merge pull request #2080 from dstufft/pr/2063

Rebase #2063