Closes #183

Squashed commit of the following:

commit c86d99a999bee9d122094df187c72af771aa77e0
Author: paulrzcz <paul@paulrzcz>
Date:   Tue Jan 28 13:46:19 2014 +0100

    Redis: version bump to 0.2.0

commit 3b6f123c135240834e337d354016ca9c3fa3fe2b
Author: paulrzcz <paul@paulrzcz>
Date:   Tue Jan 28 13:41:04 2014 +0100

    Redis: code clean up

commit 81858497e960ab0b6c3d8751243d26bb2f5b8e4c
Author: paulrzcz <paul@paulrzcz>
Date:   Tue Jan 28 13:26:23 2014 +0100

    Redis: binary serialization - test passed

commit a73f89f6624193042504aeffc75b2c5327c744d4
Author: paulrzcz <paul@paulrzcz>
Date:   Tue Jan 28 11:11:36 2014 +0100

    Redis: PersistValue binary instance

commit 460993cd2dcf3be1c0e7578d856581039ae0a2f3
Author: paulrzcz <paul@paulrzcz>
Date:   Tue Jan 28 10:49:47 2014 +0100

    Redis: time and null parsing

commit dfc3f1876fa0298891f9e2f098795e702f4313c4
Author: paulrzcz <paul@paulrzcz>
Date:   Thu Jan 23 12:53:47 2014 +0100

    Minimal version of binary serialization by binary package
Closes #206

Squashed commit of the following:

commit d27589ce4464d3cbda612635027f24f40daf8de3
Author: paulrzcz <paul@paulrzcz>
Date:   Tue Jan 28 23:20:55 2014 +0100

    Redis: no Binary orphan instance in Internals
persistent-test: Fix build.
development.md : Document backend testing with persistent-test.
Merge pull request #208 from erikd/master

Minor improvement to development docs and a build fix
persistent-test: Beef up 'Migration : is idempotent' test.

The original "is idempotent" test did not include any Unique constraints.
Adding such a constraint make this test fail.

Also worth running an "is idempotent" test more than once :-).
redis: support of aeson 0.7.0 for issue #197
redis: fixed test suite to work with aeson 0.7 for #197
persistent-postgresql: Fix #204.

The SELECT statement which read the constraints for the table had a
component:

     AND c.ordinal_position=1

which meant that when reading the constraint, only the first constraint
was read so that when it compared what was read with the schema the
migration code decided to DROP the existing constraint and then ADD the
correct constraint.

The fix is simply to drop the above line from the SELECT.
Merge remote-tracking branch 'origin/master'
version bump mongoDB for aeson
ignore cabal sandbox
existence of a nullable field should be optional

In MongoDB it already is except for embedded entities.

In MongoDB it saves space to have a non-existent field
rather than a null.
In addition, it avoids the need for a migration when adding a nullable
field.
Merge pull request #211 from yesodweb/embedded-nulls

existence of a nullable field should be optional
Use redis-server on Travis #210
Reduce number of Text to String and String to Text conversions.

Basically try to avoid String whereever possible.
Merge pull request #212 from erikd/master

Reduce number of Text to String and String to Text conversions.
Version bumps
Add bug-reports to .cabal files
Merge pull request #216 from spl/cabal-bug-reports

Add bug-reports to .cabal files