Merge branch 'v0.10.20-release' into v0.10
Now working on 0.10.21
blog: Post for v0.10.20
doc: link to pre-built binaries, add install note

lLnk to http://nodejs.org/download/ and add a short primer on how to
extract the tarballs.

Fixes #6292.
doc: add warning to fs.exists() documentation

Warn against the open-if-exists anti-pattern, it's susceptible to
race conditions.
fs: fix fs.truncate() file content zeroing bug

fs.truncate() and its synchronous sibling are implemented in terms of
open() + ftruncate().  Unfortunately, it opened the target file with
mode 'w' a.k.a. 'write-only and create or truncate at open'.

The subsequent call to ftruncate() then moved the end-of-file pointer
from zero to the requested offset with the net result of a file that's
neatly truncated at the right offset and filled with zero bytes only.

This bug was introduced in commit 168a5557 but in fairness, before that
commit fs.truncate() worked like fs.ftruncate() so it seems we've never
had a working fs.truncate() until now.

Fixes #6233.
dtrace: backport two byte string fix

This is a partial backport of 5921158

Re #6309
Closes #6319
tls: fix premature connection termination

Destroying the TLS session implies destroying the underlying socket but
before this commit, that was done with net.Socket#destroy() rather than
net.Socket#destroySoon().  The former closes the connection right away,
even when there is still data to write.  In other words, sometimes the
final TLS record got truncated.

Fixes #6107.
blog: Remove wp-to-markdown script
doc: addon: fix object instantiation examples

* Extend examples to show how to handle non-constructor invocation in
  constructor callback functions.

* Fix up examples to initialize member variables at object construction.

* Fix up a few naming inconsistencies.

Fixes #5701.
doc: net: remove bad net.Server description

net.Server is not an instance of net.Socket so don't say it is.
test: use proper findjsobjects output format

Closes #6329
doc: document os.loadavg() behavior on windows

The load average is a very UNIX-y concept.  That's why os.loadavg()
always returns zeros on Windows.  Mention that in the documentation.
util: format as Error if instanceof Error