SBT/JVM options: Add '@'-trick and #-style comment
fix broken `-no-share`
sbt 0.12.4, 0.13.0-RC1
Always prepend residual_args with 'shell' in interactive mode
upgrade SBT to 0.13.0-RC4
Merge commit 'refs/pull/54/head'
Merge commit 'refs/pull/43/head'
sbt 0.13.0 final
Purged sbt snapshot code.

And more misc tweaks. Worked around apparent sbt bug where
"++ version" is not recognized unless it comes after the
command to add the snapshots resolver.
Add '-211', update '-210' and fix README
Only install and use 0.13.0+ launchers

Prior to this change, `~/.sbt/launchers/0.13.0/sbt-launch.jar` could be
pemanently "spoofed" by an other launcher version, if sbt-extras is
first executed for another version than 0.13.0.

Since -sbt-beta (milestone) and -sbt-snapshot options have been recently
removed, I also stongly simplified the helper functions, like
'make_url'.
Merge pull request #59 from gildegoma/update-latest-scala-versions

Add '-211', update '-210' and fix README
Merge commit 'refs/pull/58/head'

Conflicts:
	README.md
Routing ++$version through the same place.
Made parser forgiving of spaces in build.properties.

Who knew that "foo = bar" is legal too. What a failure we are
as a profession that in 2013 I am writing a buggy parser for a
simplistic key/value format in bash. How many things are wrong
with that sentence.
Deleted a bunch of stuff.

There was a lot in this repo which wasn't my thing and which had
gone unmaintained the instant it arrived. I will never allow that
sort of thing to happen again. At this time there are at most two
files of interest in this repository, ignoring readmes and licenses.
Now those are the only two.
README fix
Line wrapped the license.
Some tweaks to the default jvm options.
A little more option tweaking.