fix wicked_pdf_asset_path in Rails 4 with asset_host enabled

(https://github.com/mileszs/wicked_pdf/issues/284)
ruby1.8.7 hash syntax
Merge pull request #286 from chab/master

fix wicked_pdf_asset_path in Rails 4 with asset_host enabled
Set Protocol when asset_path(source) starts with // indicating a protocol relative URL
This also provides an option to change a default protocol.
Minor Refactor to allow easier testing of asset_pathname.
Adding test for protocol relative url.
Merge pull request #287 from rposborne/protocol-less-url-support

Set Protocol when asset_path(source) starts with // (no protocol)
add --image-quality flag support
Merge pull request #292 from speranskydanil/master

add --image-quality flag support
Update README for image_quality option
Add ability to pass HTML or Pathname to :cover option

`wkhtmltopdf` accepts a "cover" option that you can pass in a URL or
html file into.

This change allows the `:cover` option to be specified in any of the
following ways:

    cover: 'http://example.org'

    cover: Rails.root.join('public', 'pdf', 'pdf_cover.html')

    cover: 'I AM COVERED'

    cover: '<html><head><body>I AM COVERED IN HTML</body></html>'

    cover: render_to_string('reports/cover.pdf.erb')
Merge pull request #296 from unixmonkey/cover_html

Add ability to pass HTML or Pathname to :cover option
Update VERSION to 0.10.0
Explicitly check for Pathname

If the cover was html that included the Rails file path
(which is likely if it includes a wicked_pdf_*_helper),
this would incorrectly assume it to be a url or filename
instead of HTML content.
Update VERSION to 0.10.1
Check argument, not arg

If argument is a Pathname, arg is Pathname#to_s
Update VERSION to 0.10.2
Add the ability to create pdf from existing files in the filesystem without converting it to HTML
Print the chosen path when file does not exists

aids debugging on server
Merge pull request #306 from masterkain/patch-1

Print the chosen path when file does not exists
add :viewport_size option
fix identation in readme