Increase version number to 1.3.1
Format plugin file

Ran file through PHP Tidy to increase readability. Used Allman (BSD)
style to normalize indentation and clean up spacing.
Format plugin whitespace, operators

Manually formatted whitespace, operators, and control structures to be
consistent throughout the plugin.
Update add_options_page call with capability

Numeric capabilities are deprecated since WP 2.0. Replaced with string
capability.
Fix HTTPS check

Some servers (XAMPP) do not define $_SERVER['HTTPS'] if connection is
unencrypted. Added a check to prevent PHP warnings.
Fix undefined constant 'on' warning

Changed "on" constant to a literal.
Fix undefined variable post_image

Ensured post_image is set when there are no images in the feed.
Update README

Documenting PHP 5.3+ requirements
Merge pull request #4 from ContentLEAD/dev-1.3.1

Merging in dev changes for v1.3.1