Merge 9to5mac version features

[adamsilverstein]

Complete changes from 9to5 in this PR, these need some reviewing & testing before merging into the plugin.

[adamsilverstein]

• XSS prevention - switch from .innerHTML to text
• alignment cleanup
• strict comparisons for in_array
• end comment sentences in periods
• pass and use post id in opted_into_auto_tweet, fixes an issue for scheduled posts
• array alignment
• check that all _GET parameters exist before using
• ensure tweet meta updates works as expected, deleting values first before setting
• escape all output
• sanitize all input
• avoid retweeting when updating published posts
• double check post is valid before tweeting
• pass and use post id in status_update
• improve inline docs
• rename Publish_Tweet helper class file
• Fix include paths, strict equality checks

[ryanwelcher]

@adamsilverstein looks awesome. Just wondering if there should be some kind of admin notice if there is an issue authenticating Twitter?

[ryanwelcher]

Small thing here but I think the package should match the namespace that this class in. In this case TenUp\Auto_Tweet\Core perhaps