Update docs badge in README

Update the URL of the docs badge to include it from inch-ci.org instead of inch-pages.github.io (the former being the successor of the Inch Pages project).

[ci skip]
Rails.application.eager_load! instead of require

Fixes #1520
Merge pull request #1576 from printercu/patch-1

Rails.application.eager_load! instead of require
replace File.exists? with File.exist?

File.exists? has been deprecated since Ruby 1.9.2
Made indentation properly
Merge pull request #1578 from dilipror/master

Made indentation properly
Merge pull request #1575 from rrrene/patch-4

Update inch-ci docs badge in README
Fix the errors happening on Travis
Converted some be_trues and be_falses
Add a test case for protocol-relative URL
Adds AttachmentSizeValidator usage example.

Syntax is not clear from current documentation.
 Replace drop_attached_file with remove_attachment
 as the former is deprecated and throws a warning.
Fixed the number helper condition issue
Another ActiveRecord -> ActiveSupport, as previous
v4.2.0
Updated NEWS for v4.2.0
Addressing issue #1593, removing calls to rebuild class
Allow #original_filename= to receive nil argument