Revert "removed a debug logging call; return early from is_signup() if we already have the value of $this->is_signup"

This reverts commit 3e75ce50dd08fc4a6482b1a4895cff7c42bb4a97.
Revert "added a function to check if we're on the configured sign-up page or not"

This reverts commit d0c1156b52ad2b65eb4a7657b925cd81122c82b3.
Merge pull request #22 from wluo/github-4055

reverted the is_signup() function
* get the converted post id with the 'go_subscriptions_converted_post_id' filter
* removed the restriction that only go-subscriptions can set read_post and read user caps
validate converted post id so we don't get the id of a page or non-single-page posts. see https://github.com/GigaOM/legacy-pro/issues/4353
Merge pull request #24 from wluo/github-4353

validate converted post id
changed the 'go_subscriptions_converted_post_id' filter to 'go_subscriptions_thankyoucta' to customize the button cta on the thank you page.
Merge pull request #23 from wluo/freebird-v2

get the converted post id with the 'go_subscriptions_converted_post_id' filter
use rawurlencode instead of urlencode to make sure spaces are encoded correctly in query vars. see https://github.com/GigaOM/legacy-pro/issues/4370
Merge pull request #25 from wluo/github-4370

use rawurlencode instead of urlencode to make sure spaces are encoded correctly in query vars