Renames temp directory and removes it in release builds. Refs #28.
Implements #41.

Also, building of binary packages now takes place before any old packages
are removed. This is to prevent the case where the old package is removed
and a new version of the same package fails to build so the user is left
with no package at all.
Merge branch 'pr_removes_tmp_directory' of https://github.com/gradha/babel into gradha-pr_removes_tmp_directory

Conflicts:
	src/babel.nim
Merge branch 'gradha-pr_removes_tmp_directory'