setup.py: install *.rst files instead of *.txt, trying to fix #279

It seems that since commit 8e0d3bb5 txt documents are rewrited using
restructured text, but setup.py wasn't updated to install them.

This commit updates setup.py to install files with rst extension
instead.

Signed-off-by: Ｖ字龍(Vdragon) <pika1021@gmail.com>
Merge pull request #280 from Vdragon/fix_missing_rst

setup.py: install *.rst files instead of *.txt

Closes #279

Signed-off-by: David Aguilar <davvid@gmail.com>
doc: update v2.0.4 release notes draft

Signed-off-by: David Aguilar <davvid@gmail.com>
bookmarks: improve usability in the context menu

The "Edit" action was really "Launch Editor", so the menu action
explicitly to avoid ambiguities.

Add a new "Edit" action that actually edits the bookmarks list, which is
what most users would expect when clicking on "Edit".

Closes #281

Reported-by: Ｖ字龍(Vdragon) <pika1021@gmail.com>
Signed-off-by: David Aguilar <davvid@gmail.com>
compat: support unicode in environment variables

On Python2 we have to encode provide utf-8 bytestrings if we want
unicode values in enviornment variables.  Python3 accepts them as-is.

Related-to: #282
Reported-by: Ｖ字龍(Vdragon) <pika1021@gmail.com>
Signed-off-by: David Aguilar <davvid@gmail.com>
git-{cola,dag}: support installation prefixes with utf-8 paths

Decode the bytestring so that os.path.join() can operate on it now that
we're using unicode literals.

Closes #282

Reported-by: Ｖ字龍(Vdragon) <pika1021@gmail.com>
Signed-off-by: David Aguilar <davvid@gmail.com>