Allow configuring the Nginx `location` setting via an attribute

Closes #218
Added traling slash to `proxy_pass` configuration to play nice with custom `location`

Related: #218
Allow configuring the Elasticsearch's installation `bindir` via attribute

Removes "magic path". Closes #216
Added new attributes for configuring the env.sh and .yml templates locations

This should make it easier for people to override these values "from the top",
eg. in a wrapper/application cookbook, similarly as the Varnish cookbook does it:

--> https://github.com/opscode-cookbooks/varnish/blob/master/recipes/default.rb

Closes #153
Added `uid` and `gid` attributes for the ElasticSearch user

Closes #211
Release 0.3.10
Fixed removal of stale PID file in the init script

Closes #229
Related #224
Moved computation of `dowload_url` to the recipe

This prevents a number of errors and surprises when setting the Elasticsearch version.

If the user overrode the node.elasticsearch[:version] property, the download directory and symlinks would be
created with the correctly overridden version number. However, the download URL would be computed with
the default version number, and thus the incorrect, default version of elasticsearch would be installed.

Since there's no need to compute the download filename and URL until node convergence, this patch moves that computation to the default.rb recipe. However, the node.elasticsearch[:filename] and node.elasticsearch[:download_url] attributes, if present, are respected and given preference upon node convergence, so that users still have the capability to override these attributes and thus configure downloads from a custom repository.

Related: #100, #180, #178, #240, #179, #245, #227, #245

Closes #242
Release 0.3.11
Added the `plugins.json` data bag for testing

Related: #246
Merge branch 'master' of github.com:elasticsearch/cookbook-elasticsearch