Added test:all and test:all:db tasks to speed up full test runs.

Speed up depends on the number of test phases (N) you have for your
app, but it is roughly a 1/N improvement. In my app, it goes from
15.51s to 5.56s.

Inspired by http://ngauthier.com/2012/02/quick-tests-with-bash.html

Reviewed by @tenderlove
Merge pull request #9177 from zenspider/master

Added test:all and test:all:db tasks to speed up full test runs