blog: Post about v0.9.4
lint
build: allow to specify custom tags

When building custom `node` versions (e.g., floating features/fixes from
different versions) it's often useful to specify a custom tag which
easily identifies build when invoking `node -v`.

Introduce a way to specify this tag in `node_version.h` file or by
running `./configure --tag="<tag>"`. Insert it right after the patch
version (and before `-pre`, if build is not a release).
deps: upgrade libuv to 4997738
blog: Post for v0.9.5
doc: add CONTRIBUTING.md
os: change CPU time from Integer to Number

CPU time values must be Numbers, not Integers, as they can be too large
for Integers on 32 bit platforms.
Merge remote-tracking branch 'origin/v0.8'