Removing wiki repo submodule

"doc is dead, long live docs"

All of the content formerly in the doc directory is still part of the
wiki and nothing is getting deleted in this commit.  This commit just
deletes the submodule pointer from the Titan repo to the Titan wiki
repo.
Adding automated version compat test

This is for #473

This commit adds new tests and release scripts and pom snippets to
support automatic forward-compatibility test cases.  Each time Titan
releases, it now loads GraphOfTheGods into BDB+ES, then zips the
BDB+ES files into an archive and uploads it to S3.  The release
process also appends the HTTP URL pointing to the zipfile in S3, along
with a couple of other metadata fields, to the compat.csv file created
in this commit.  All subsequent releases iterate over the lines in
this file and check that the current release can open and query the
copy of GotG created by that old version.  The open+query test is uses
Expect and borrows queries from the Getting Started section of the
docs.

I initially tried to tie all of this into maven-release-plugin's
configuration, but I ran into limitations around committing files
during release:prepare:

https://jira.codehaus.org/browse/MRELEASE-798

I added a new helper script, commit-compat-version.sh, and updated
RELEASING.md accordingly.  However, RELEASING.md has accumulated quite
a few steps.  It's up to seven just to stage the release artifacts and
stop just short of releasing Sonatype to Central and pushing commits
and tags to github.  I created a new script to automate these steps
named release.sh.  This prompts the user to update
titan.compatible.versions, then carries out all of the release steps
through `mvn deploy`.  It stops just short of the point of no return;
it doesn't push commits/tags to github or release artifacts to
Central.

I tested this by locally running the release steps for 0.5.1 and
0.5.2, but skipping the points of no return and deleting the staged
artifacts after testing.

I lost count of how many times I amended this commit before pushing.