changed 'trigger method' to 'trigger view event'

button helpers can have both a method="" and trigger="". Method calls a method on the corresponding view, trigger triggers an event on the corresponding view.
Fix minor grammar typo
It's -> its

Corrected instances of "it's" used incorrectly where "its" is needed.
Looked through all the .md files, I hope I didn't miss anything.

Changed both individual chapters and the merged complete book one, not
sure how "backbone-fundamentals.md" is generated.
Merge pull request #479 from encryptedcommerce/gh-pages

fixed minor typo, enabled validation in jsfiddle code
Merge pull request #478 from kryger/gh-pages

It's -> its
Merge pull request #476 from vkurup/patch-1

Fix minor grammar typo
Merge pull request #475 from colinmegill/patch-2

changed 'trigger method' to 'trigger view event'
Updating cover, adding intro comment to page, compiling fresh build with latest changes
Fixes #462 - fixes understanding render
Pushing fresh build
Merge remote-tracking branch 'upstream/gh-pages' into gh-pages