Hooks VCR into webmock rather than fakeweb.

Mostly to avoid VCR's deprecation warnings!
Refactors Sources/Books to Books for extra ducktyping.
Refactors CloudNote/EvernoteNote to EvernoteNote and CloudService/Evernote to EvernoteAuth.

For increased ducktyping.
Tidies up formatting.
Does all formatting and sanitization of body copy on output.
Adds better rescue from error when fetching book metadata from APIs.
Tweaks Development environment.
Adds BookMailer tests.

Omitted from last commit.
Puts rails_admin at the bottom.

Tries to fix a bootstrap-sass problem that only occurs when Travis CI is
running RSpec tests.
Adds secret_token to secret file.
Updates styling of notes and citations.
Updates gems.
Fixes crop/resize and gravity.
Fixes #author_surname.
Fixes captions, descriptions, credits.

Since we're reading straight from Evernote data we use <div> and </div>
rather than ^ and $ as line delimiters. If we end up using a sanitized
version of the body for other uses (e.g. wordcount), then we can use
that.
Updates styling colours.
Minor mark-up fixes.