Remove EmberConf callout.

As requested by @wifelette, since EmberConf is current sold out do not
display the logo/link on the homepage.
Fixed typos
Added adding-google-analytics-tracking to the index
Merge pull request #1292 from emberjs-cn/patch

Patch
Add note to registerHelper section

Helpers must be registered before injecting the test helpers.
Merge pull request #1295 from kategengler/patch-1

Add note to registerHelper section
adds orchestrate.io as ember user