add jruby test
Fix warning warning libjffi-1.2.so on < JRuby 1.7.3

[JRuby Issue](https://github.com/jruby/jruby/issues/899). We need to use
an older JDK for JRuby 1.7.3 and lower.
update changelog
Merge pull request #168 from heroku/jdk_u40_update

Fix warning warning libjffi-1.2.so on < JRuby 1.7.3
v83
print out the proper JDK being installed
fixes very small typo

  - `flushing` was missing the `h`
Merge pull request #170 from xentek/patch-1

fixes very small typo
Fix default gem cache
Merge pull request #173 from heroku/schneems/fix-default-cache

Fix default gem cache
v84
Increase curl timeout to two minutes

In #165, a few users are getting time outs.

```
  Compiling Ruby
 !
    ERROR: Command: 'set -o pipefail; curl --fail --retry 3 --retry-delay 1 --connect-timeout 3 --max-time 20 https://s3-external-1.amazonaws.com/heroku-buildpack-ruby/ruby-1.9.3-jruby-1.7.3.tgz -s -o - | tar zxf -' failed unexpectedly:
    ERROR: 
    ERROR: gzip: stdin: invalid compressed data--format violated
    ERROR: tar: Unexpected EOF in archive
    ERROR: tar: Unexpected EOF in archive
    ERROR: tar: Error is not recoverable: exiting now
 !
```
Use hobby-dev as default db
Merge pull request #179 from catsby/default_postgres_plan

Use hobby-dev as default db
make curl max_timeout variable with env.
[fix #171] Refactor Rake Detect and Run

Move rake task detection and running to a separate independently tested class.

Compile exits when rake tasks cannot be successfully detected with error message
Merge pull request #172 from heroku/schneems/better-rake-detect

[fix #171] Refactor Rake Detect and Run
[ci skip] Changelog
[fix #182] Show Warning In-line for Windows Gems

When deploying a Gemfile.lock that has been generated via windows, we must remove the file which can cause bundler to not be able to resolve.

When bundler does not resolve, the end user never sees the windows warning message due to the resolver never finishing (since warnings are saved until the end of the output).

This change allows warnings to be emitted inline and changes the default behavior of the windows warning to display before the `bundle install` is run, thus mitigating this problem.

Even when the `bundle install` fails the warnings are not displayed since the process `exits` rather than continues to print out the warnings.

Here is a link to the devcenter article I wrote for this PR https://devcenter.heroku.com/articles/bundler-windows-gemfile
Fix year in changelog