Lots of documentation cleanup

Lots of documentation cleanup

- fix the new navbar and page titles
- update the "hacking" page, remove the obsolete
  "buildbot" and "source" pages
- remove TODOs and old project info from the
  "language specification" page

R=scottmg@chromium.org
BUG=481696
Committed: https://chromium.googlesource.com/external/gyp/+/a69455b4a08ad8ec16ba0b249f2d3c0a1237dfc9

[Dirk Pranke, 2015-08-13 22:50:05]

This is a bit more substantive.

In addition to fixing the nav bar, I remove a lot of the obsolete stuff related
to the project launch 7+ years ago, and a lot of the TODO(sgk)'s that probably
aren't going to happen by sgk at this point :)

[scottmg, 2015-08-13 23:06:41]

lgtm

https://codereview.chromium.org/1292053003/diff/40001/docs/GypVsCMake.md
File docs/GypVsCMake.md (right):

https://codereview.chromium.org/1292053003/diff/40001/docs/GypVsCMake.md#newc...
docs/GypVsCMake.md:32: substantial period of time, we had a hybrid of checked in
vcproj and gyp generated
80 col for these two I guess

https://codereview.chromium.org/1292053003/diff/40001/docs/Hacking.md
File docs/Hacking.md (right):

https://codereview.chromium.org/1292053003/diff/40001/docs/Hacking.md#newcode70
docs/Hacking.md:70: git cl try -use-buildbucket
is this not `--use-buildbucket`?  (2 leading, not 1)

[Dirk Pranke, 2015-08-13 23:27:04]

Committed patchset #3 (id:40001) manually as
a69455b4a08ad8ec16ba0b249f2d3c0a1237dfc9 (presubmit successful).

[Dirk Pranke, 2015-08-13 23:29:47]

patchset #4 is actually what got committed.