README: Timing measurements for a *release* build of libclang

This is very embarrasing: I had been measuring against a debug build of
libclang. With a release build, the picture is not so grim (though still
a far cry from the sub-second times of traditional ctags/etags).
README: Document processing time increase with --all-headers and --non-system-headers

Also document the possibility of parallelizing clang-ctags to make use
of multiple CPUs.
--suppress-qualifier-tags is now the default behaviour

Use --extra-qualifier-tags to re-enable this behaviour. The option
--suppress-qualifier-tags remains, but has no effect and will be removed
in a future release.

With the old default, the generated tag files were large enough (60MB+)
to cause my editor (Emacs) performance troubles with fuzzy matching
enabled; and for the user the sheer number of matching tags (in the
tab-completion list presented by Emacs) was often overwhelming.
Update version to '0.2'
README: Add "-e" flag to invocation example

clang-ctags doesn't currently support vi-style tags (without the "-e"
flag).
README: Mention "Build EAR", a tool to generate the compilation database
run-tests.sh: Ignore user's GREP_OPTIONS

My .bashrc sets `GREP_OPTIONS=--exclude=TAGS`, which was causing
`assert_tag` to always fail.
Ctags (Vi) format

TODO:

* Add tests (figure out how to get vi to output filename & line number
  to stdout, for integration tests).
* Sort the tags?