Clean up forms

Add a small library to handle forms. This should make it a lot easier
to modify the form in the future as well as for other people to add
their own forms
Add action so we can delete transients
Merging v0.4 bump
Replace `update_transient()` with `set_transient()`
Output previous textarea value in the export form
Change visibility of `VIP_Scanner_Form::delete_transient()` as it's called in a hook and must be public
Merge branch 'UI-Refresh'
Fix previous value on error_summary - check that it's set before using it to prevent notices
Rework the conditional 'error summary' field

Use the VIP_Scanner_Form::add_field() api instead and make it optional.

Currently there is no good way to do conditionally required fields in
VIP_Scanner_Form. The approach here was causing all fields to be
emptied out on an invalid POST, since it reset the transient.

Since there is no good way to do this currently (I struggled against it
for several hours), we can just make it optional for now and ding
anyone that fails to provide an explanation.
Update error levels for a variety of checks

Removes false positives for things like working with cache and options
(lowers the message to a Note).

Escalates a variety of file related operations and `query_posts()` to
blocker.
Remove the head 'profile' attribute check

profile is deprecated in HTML 5, let's skip the check.

Fixes #32
Flag uses of filter_input() - should use sanitize_* instead

Fixes #11
Flag uses of WP_Widget_Tag_Cloud, which does not exist on WordPress.com

Use WPCOM_Tag_Cloud_Widget instead

Fixes #15
Merge pull request #30 from natebot/master

Prevent false positives when using vip_powered_wpcom() for attribution

props @natebot
Merge pull request #33 from natebot/master

Linking to documentation in note for test for vip_powered_wpcom.

props @natebot
Update contributors
Updating changelog with recent changes
Flag all session functions in VIP themes

Fixes #39
Flag uses of create_function()

create_function() is generally bad practice.

Fixes #37
Flag uses of extract()

extract() sucks.

Fixes #35