docs: fix links and typos

Update stale/broken links.  Use consistent link style:
 - links between our files should relative
 - omit filename for links within same file
 - don't specify heading id
Don't use same heading twice in one file because the markdown compilers
on googlesource.com and github have different ways of disambiguating them,
so this is the easiest way to have links work on both sites.

BUG=angleproject:1569

Change-Id: Iefd5ab8014d582a017f64e383f301ea0b8e60433
Reviewed-on: https://chromium-review.googlesource.com/789445
Reviewed-by: Yuly Novikov <ynovikov@chromium.org>
Reviewed-by: Geoff Lang <geofflang@chromium.org>
Commit-Queue: Frank Henigman <fjhenigman@chromium.org>
diff --git a/README.md b/README.md
index 91a4744..daff77a 100644
--- a/README.md
+++ b/README.md
@@ -55,13 +55,13 @@
 
 * Join our [Google group](https://groups.google.com/group/angleproject) to keep up to date.
 * Join us on IRC in the #ANGLEproject channel on FreeNode.
-* File bugs in the [issue tracker](http://code.google.com/p/angleproject/issues/list) (preferably with an isolated test-case).
+* File bugs in the [issue tracker](https://bugs.chromium.org/p/angleproject/issues/list) (preferably with an isolated test-case).
 * [Choose an ANGLE branch](doc/ChoosingANGLEBranch.md) to track in your own project.
 
 
 * Read ANGLE development [documentation](doc).
-* Look at [pending](https://chromium-review.googlesource.com/#/q/project:angle/angle+status:open)
-  and [merged](https://chromium-review.googlesource.com/#/q/project:angle/angle+status:merged) changes.
+* Look at [pending](https://chromium-review.googlesource.com/q/project:angle/angle+status:open)
+  and [merged](https://chromium-review.googlesource.com/q/project:angle/angle+status:merged) changes.
 * Become a [code contributor](doc/ContributingCode.md).
 * Use ANGLE's [coding standard](doc/CodingStandard.md).
 * Learn how to [build ANGLE for Chromium development](doc/BuildingAngleForChromiumDevelopment.md).