Move specs to a rapgenius subfolder

`lib/rapgenius/foo.rb` should have a `spec/rapgenius/foo_spec.rb` file.
Add webmock and vcr as development dependencies
Add VCR configuration
Drop webmock requirement to 1.11.0

VCR spits out a warning about higher versions. It still seemed to work
but I hated seeing the message.
Update Song's spec

- Replaced `:fetch` stubbing with VCR cassettes
- Removed unneccessary testing of the `find` method.
- Broke some one-liner tests into `describe` blocks where there was a
  clear relation between multiple tests.
Refactor Scraper#url= a bit
Minor reorganization of Scraper; update Scraper specs

Introduces a 'Client' class that includes HTTParty and then sets some
sane defaults for all of the lib's requests. I kept the Scraper module
in tact and just updated it to use this new Client class so that
`include RapGenius::Scraper` in Song and Annotation still worked.

Where possible I kept everything the same for backwards-compatibility
until @timrogers wants to change things.

Also updated are the specs for the module. Removed some specs that were
basically testing low-level HTTParty stuff.
Update Annotation's spec
Merge pull request #6 from tsigo/vcr

Spec reorganization and updating
Updates version to 0.0.3 with changelog
No more Gemfile.lock in commits
Adds .gem package for 0.0.3
Fix annotation spec broken by live site data
Song searching
Add Song searching to README
Merge pull request #7 from tsigo/song_search

Song searching
Updates to v0.1.0 with search
Remove the 0.1.0 package so I can make it again...
Add license info to README and gemspec.

Closes #8