Improve I18N Issues (Based on 1.1.6)

There are some I18N issues for this plugin, I list them for your reference.

• This “Requires at least” is below 4.6. so you need to set a Text Domain in easy-footnotes.php, and it needs to be easy-footnotes to correctly internationalize your plugin! Please refer to this official article.
• Requires at least (3.0.1) is below 4.6, so a load_plugin_textdomain is needed. Please make sure you load it at a certain point in your plugin. Please refer to this official article.
• easy-footnotes-admin.php, line 61 should be the following.

<input type="submit" name="Submit" value="<?php esc_attr_e( 'Update Options', 'easy-footnotes' ); ?>" />