Compress images

Compress images using
[ImageOptim](https://github.com/pornel/ImageOptim) version 1.4.3
Merge pull request #65 from pathawks/master

Compress images
Adding some helpful filters here and there.
Allow third-party plugins and addons to override any CampTix e-mail with a filter.
Use .get instead of .getByCid which was removed from collections in Backbone 0.9.9
Allow payment_checkout() to return HTML.

Before we assumed that payment methods would either redirect or return an error during payment_checkout(),
but turns out some payment providers need an extra step to show some HTML to the user during checkout.

Props @nb
Add searching for and order by attendee.

Some payment providers could make good use of the attendee IDs, so
give them a helper function to retrieve the order array by that ID.

Props @nb
Urlencode reservation ids

Currently, if a reservation name contains special characters for a URL,
the reservation URL won't work and we will get "Sorry, but the
reservation you are trying to use seems to be invalid or expired."

That's because sanitize_title_with_dashes urlencodes the data,
but all the request variables are automatically decoded and when we
compare them they don't match.
Extract reservation creation in a method
Use a random reservation token

The pseudo-crypto-random token can be guessed pretty easily, since most
of the information is public or not very hard to obtain.

Props @guille
Merge pull request #70 from nb/random-reservation-token

Use a random reservation token
Merge branch 'master' of github.com:Automattic/camptix
Don't sanitize reservations ids and tokens

sanitizer_text_field removes urlencoded %-based octets, which are
sometimes valuable information. In our case – we have token ids in
Cyrillic.
Fix some string and docs typos.
Merge pull request #71 from DrewAPicture/typo

Fix some string and docs typos.
Add an action and filter in to affect the tools menu tabs and pages.
Merge branch 'urlencode-reservation-id' of https://github.com/nb/camptix into 68
Update camptix-fr_FR.po
Add a 3.8 compatible icon. Props @field2
Add [camptix_stats] shortcode.