Wrong default GEM_HOME in generated META-INF/init.rb

Was generating the following: (default config.gem_path is WEB-INF/gems though)

if $servlet_context.nil?
  ENV['GEM_HOME'] = File.expand_path('../../WEB-INF', __FILE__)
  ...

After:

if $servlet_context.nil?
  ENV['GEM_HOME'] = File.expand_path(File.join('..', '..', '/WEB-INF/gems'), __FILE__)
  ...
Merge branch 'lenny-init_rb-GEM_HOME'
updated history file [skip ci]
Include most current gem version in README

* I like to see it in one go and not go to rubygems/commits
Merge pull request #291 from PragTob/patch-1

Include most current gem version in README
Use a topological sort to order traits by requirements.

The original sort using a comparator does not work as required here. For
example, both (Rack <=> Jar) and (Jar <=> War) are 0 (since neither depends on
the other). By the rules of sort, this should imply that (Rack <=> War) is also
zero, since sort requires the comparator be transitive. However, this is not
true, as Rack depends on War.

This patch fixes this problem by using tsort, which is the appropriate mechanism
for sorting DAGs like trait requirements.
minor java code cleanup + make sure we use runtime.out to print stack traces
unify debug/error prints + align Java code-style
require 'newer' jruby-rack (at least 1.1) and set an upper version bound for it as well
default to webserver = 'jetty' (instead of winstone) with the executable war archive
improve web server jar caching (into maven's local repository)