Conflicting plugins: add Related Posts plugins to the list

See #170 for more details
Facebook Like Box: Fix default and minimum width.

In 4a3d04a5dafe401a2, the default and minimum width of the widget were
changed to reflect the Facebook documentation. However, this caused some
problems.

I have tested and it turns out the documentation is not true. Despite
the documentation claiming the widget has a minimum width of 292, in fact
a lower width will be respected. The actual minimum width appears to be
around 150 or so, but I will just set it back to 0 as it was before.

Reported by Elizabeth Urello (eurello).

Merges r90761-wpcom.
Tiled Galleries: use alt value instead of title for alt attribute

I added alt attributes to Tiled Galleries in e75fecaa818a3c84fcc9b64e729fe300bad869c0
but should have use the actualy image alt instead of the image title
Jetpack: Fix strict standards warning that shows on Jetpack::register() post php 5.4
Merge branch 'master' of github.com:Automattic/jetpack
PHP 5.3 crashes if `method_exists()` is called on a class that does not exist.

Use `class_exists()` to test for class before testing for a method within a
class. Props @gibrown
Merge pull request #196 from xyu/module-related-posts

PHP 5.3 crashes in some instances with Related Posts
Jetpack: SSO: Disallow match by email by default when logging in for the first time
Add @lettergrade to list of Jetpack HEs
GPlus Authorship: Add check for main loop.

`is_main_query()` will return true, even if outside the loop when the global `$wp_query` variable is not replaced with a different query. `in_the_loop()` will check if we're in the main loop, and set the function's return value to `false`, if we're not.
Make backspace in carousel view functional in Chrome and Firefox.

Currently, utilize backspace will cause the page URL to update properly, but the actual image does not change. This corrects this behavior in Chrome and Firefox on Windows and OS/X--pressing backspace will now return to the previous image, as expected.
Display Posts widget: close div when no posts are returned

Props @chriswallace
Merge pull request #208 from jeherve/2152-trac

Display Posts widget: close div when no posts are returned
Merge pull request #203 from pcrumm/correct-backspace-behavior

Make backspace in carousel view functional in Chrome and Firefox.
Merge pull request #193 from jeherve/tiled-alt-images

Tiled Galleries: use alt value instead of title for alt attribute
Merge pull request #192 from jeherve/170-github

Conflicting plugins: add Related Posts plugins to the list
Jetpack: Slideshow: Properly resolves and closes #180