plugin install broken if the project name have spaces

(Update)

if you run `bin/plugin install` from a directory that have spaces, then the sh script gets consufed while looking for logstash.lib.sh and can not continue.

--- Original message ---
As discovered from http://build-eu-00.elastic.co/view/LS%201.5/job/Logstash%20Regression%201.5%20(Release)/3/jdk=JDK7,label=metal-pool/console

```
Using sawyer 0.6.0
Using octokit 3.8.0
Using rubyzip 1.1.7
Using bundler 1.9.7
Bundle complete! 114 Gemfile dependencies, 194 gems now installed.
Gems in the group development were not installed.
Bundled gems are installed into ./vendor/bundle.
[plugin:install-core] Installing core plugins
/home/jenkins/workspace/Logstash Regression 1.5 (Release)/jdk/JDK7/label/metal-pool/bin/plugin: 4: .: Can't open /home/jenkins/workspace/bin/logstash.lib.sh
rake aborted!

/home/jenkins/workspace/Logstash Regression 1.5 (Release)/jdk/JDK7/label/metal-pool/rakelib/plugin.rake:7:in `install_plugins'
/home/jenkins/workspace/Logstash Regression 1.5 (Release)/jdk/JDK7/label/metal-pool/rakelib/plugin.rake:34:in `(root)'
org/jruby/RubyProc.java:271:in `call'
org/jruby/RubyArray.java:1613:in `each'
org/jruby/RubyArray.java:1613:in `each'
org/jruby/RubyArray.java:1613:in `each'
org/jruby/RubyKernel.java:1087:in `load'
Tasks: TOP => test:install-core => plugin:install-core
(See full trace by running task with --trace)
WARN: Unresolved specs during Gem::Specification.reset:
ffi (>= 0)
WARN: Clearing out unresolved specs.
Please report a bug if this causes problems.
rake aborted!
Could not find rake-10.4.2 in any of the sources
/home/jenkins/workspace/Logstash Regression 1.5 (Release)/jdk/JDK7/label/metal-pool/vendor/bundle/jruby/1.9/gems/bundler-1.9.7/lib/bundler/spec_set.rb:92:in `materialize'
org/jruby/RubyArray.java:2444:in `map!'
/home/jenkins/workspace/Logstash Regression 1.5 (Release)/jdk/JDK7/label/metal-pool/vendor/bundle/jruby/1.9/gems/bundler-1.9.7/lib/bundler/spec_set.rb:85:in `materialize'
/home/jenkins/workspace/Logstash Regression 1.5 (Release)/jdk/JDK7/label/metal-pool/vendor/bundle/jruby/1.9/gems/bundler-1.9.7/lib/bundler/definition.rb:132:in `specs'
/home/jenkins/workspace/Logstash Regression 1.5 (Release)/jdk/JDK7/label/metal-pool/vendor/bundle/jruby/1.9/gems/bundler-1.9.7/lib/bundler/definition.rb:177:in `specs_for'
/home/jenkins/workspace/Logstash Regression 1.5 (Release)/jdk/JDK7/label/metal-pool/vendor/bundle/jruby/1.9/gems/bundler-1.9.7
```

it actually complains about not properly finding the logstash.lib.sh file in https://github.com/elastic/logstash/blob/master/bin/plugin#L1-L11

This does not happen with mac. Before assessing the severity we should also check packaging is healthy.