Bubble up the offending url through the error message

Allows more comprehensive error handling through consumers of
`blue_kai_middleware`
TODO: Abstract the error handler out to work more generically with
`Faraday`
Upgrade rspec

Full `expect` support
Fixes per a first pass of BlueKai's `rubocop` settings

Current `.rubocop.yml` file:

```
# Multi-line method chaining should be done with leading dots.
DotPosition:
  Style: trailing
  SupportedStyles:
    - leading
    - trailing

MethodLength:
  CountComments: false  # count full line comments?
  Max: 15

SpaceInsideHashLiteralBraces:
  EnforcedStyle: no_space
  EnforcedStyleForEmptyBraces: no_space
  SupportedStyles:
    - space
    - no_space

Semicolon:
  # Allow ; to separate several expressions on the same line.
  AllowAsExpressionSeparator: true
```
Merge pull request #13 from BlueKai/feature/add-request-url-to-errors

Feature/add request url to errors

cr @archana-bluekai @kevinelliott