truncate PR description in backported git msg to five lines

sometimes these things are huge.
Merge pull request #5865 from takluyver/latex-test-fix

Rework Latex test for nbconvert Python API
Catch more errors from clipboard access on Windows
Merge pull request #5869 from takluyver/win32clipboard-catch-more-errs

Catch more errors from clipboard access on Windows
specify encoding in msgpack.unpackb

otherwise, it will leave strings as utf8 bytes
Use TemporaryWorkingDirectory context manager in some tests
Ensure history tests release database before cleanup
Merge pull request #5871 from minrk/msgpack-unicode

specify encoding in msgpack.unpackb
Merge pull request #5872 from takluyver/tmpdir-cleanup-errors

Tmpdir cleanup errors
Ensure history database is closed in test

Hopefully fixes the last Windows test on Python 3.3
fix undefined js_enabled on `iptest —all`
remove redundant js_enabled variable

it’s only False if the js_testgroups list is empty
Merge pull request #5875 from minrk/js_enabled

fix undefined js_enabled on `iptest —all`
Close database when HistorySavingThread stops
Merge pull request #5874 from takluyver/test-hist-close-db

Ensure history database is closed in test
use current cell's type when inserting

this preserve all previous behavior, but simply adds the ability to
insert cells without specifying a cell type, in which case the cell type
is inferred from the currently selected cell
inserting new cells preserves type  closes #4917
Merge pull request #5855 from minrk/load-after-session

ensure load_connection_file works after self.session is created
add tests for cell_type preserving insertion
Merge pull request #5882 from ivanov/preserve-cell-type

inserting new cells preserves cell type