further adapter tests, and associated fixes
adapt messages in Session

adds Session.adapt_version for target version.

- serialize adapts to Session.adapt_version (default: 0, no adaptation)
- unserialize always adapts to current active version
interrogate kernel_info to get protocol version for adaptation
update message spec adapter per review

- docs and comments
- adapt complete_reply with `end=null`, `start=-len(matched_text)`
- remove some incorrect `status` fields
- add `handle_reply_status_error` for handling `status=error` replies (no-op, currently)
Merge pull request #5752 from minrk/msgspec-adapter

Add adapter for msg spec versions
Merge pull request #5616 from echatelet/fix-4942-n

Fix 4942 (torture notebook)
Merge pull request #5353 from Zaharid/nonetraits

Allow None for most traits
Fixed example to work with python3

Just some print parentheses added.
Make rmagic display call compatible with updated API

Passing all arguments as keywords will work with the previous API as
well.

CC @davclark - You'll want to copy this change across to rpy2, because
without it, rmagic is broken with IPython master.
Merge pull request #5832 from Zaharid/ip3fix

Fixed example to work with python3
Merge pull request #5834 from takluyver/rmagic-display-fix

Make rmagic display call compatible with updated API
Refactor kernelspec resource handler to separate URL prefix
fix typo in v2 convert

resulted in NameError on orig_version because arg name is from_version
pass on install docs

there were many False statements, and no-longer appropriate recommendations to use easy_install.
Merge pull request #5837 from minrk/install-doc

pass on install docs
Close graphics dev in finally clause\ncloses #4408 (already closed)
Merge pull request #5839 from davclark/rmagic-graphics

Close graphics dev in finally clause
Add failing test for issue 2412

Writing history to a file including output fails
Fix writing history with output to a file in Python 2

Closes gh-2412
Put full kernel info in REST API response for all kernels