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
first attempt at fixing default attributes
Merge branch 'fix-attributes' of github.com:mattcl/cookbook-elasticsearch into fix-attributes