.gitignore maintenance

Signed-off-by: David Aguilar <davvid@gmail.com>
Add recent additions to MANIFEST.in

Signed-off-by: David Aguilar <davvid@gmail.com>
documentation updates

Signed-off-by: David Aguilar <davvid@gmail.com>
pickler: rename *collection* methods to *sequence*

Avoid confusion with `collection.defaultdict` and friends by renaming
these.

Signed-off-by: David Aguilar <davvid@gmail.com>
tests: remove 'import *' in util_tests.py

Signed-off-by: David Aguilar <davvid@gmail.com>
jsonpickle: do not depend on 'six'

jsonpickle.compat has everything we need.

Signed-off-by: David Aguilar <davvid@gmail.com>
jsonpickle v0.5.0

Signed-off-by: David Aguilar <davvid@gmail.com>