Add has_secure_password to list of keywords.

Rails 3.1 adds new class method called has_secure_password. This is a
class method and should be highlighted as such.
This commit adds the has_secure_password to list of keywords in
rails.vim.
Don't put tmux window in background

Some contributor made the decision to do this, which seems pretty silly
to me.
Needs to detect spec-lib before it detects lib
Support direct mapping between app/* <-> test/*

In fact, I went as far as making it the first one on the list, so it's
hinted that it's the new way.
Correct documentation grammar
Merge pull request #170 from DawidJanczak/master

New has_secure_password method
Source app specific config earlier

This will let us set buffer local variables to influence navigation
command creation and other behaviors.
Don't source app config if modelines are disabled

Both modelines and app specific config have the same security risks.
Allow defining per-app navigation commands

Closes #195.
Render string for slim template
Simplify define_navcommand interface
Add support for config/editor.json

Not yet documented.  This is intended to ultimately replace
config/rails.vim.
Support custom "classifications" in config/editor.json

A classification is a category of file in your app: model, controller,
helper, and so forth.  You can now provide custom classification
definitions in your application's config/editor.json and they will be
automatically defined as navigation commands.  Example config:

    {
      "classifications": {
        "concern": {
          "prefix": "app/concerns/",
          "suffix": ".rb"
        },
        "fabricator": {
          "alternate": "app/models/%s.rb",
          "affinity": "model",
          "prefix": ["spec/fabricators/", "test/fabricators/"],
          "suffix": "_fabricator.rb"
        }
      }
    }

The "affinity" attribute lets the classification receive and provide
default arguments.  With this example, one could use :Rmodel in a
fabricator to jump to the model, and vice versa.

The "alternate" attribute provides the destination for the :A command.

Suggestions for alternative names for "classification" (and "affinity")
welcome.  "Type" is a confusing choice because Vim already has file
types.
Add support for abbreviations in config/editor.json

The sky's the limit as to what we can support here.  What else?
Refactor navigation command definition
Don't require trailing slash in prefix
Fix typo
Remove dumb comments
Undocument -default=both()

This was dumb.
Dogfood navcommand creation

Many of the built-in navigation commands have special behavior that
aren't currently accounted for in the publicly exposed interface.
That's fine.