docs(ngClass): Explain all 3 ways how to use ngClass

Closes #6324.
fix(jqLite): make jqLite('<iframe src="someurl">').contents() return iframe document, as in jQuery

This is a very tiny change to make behaviour consistent with jQuery.

Closes #6320
Closes #6323
style(jqLite): remove trailing whitespace in new test

Oops.
chore(travis): don't run Travis-CI builds for G3 branches

Building the G3 commits occupies a lot of time, and these branches have
already been tested.

Closes #6328
docs(guide/providers): fix example snippet

Closes #6331
Closes #6332
docs(triaging): remove reference to the obsolete chrome extension
docs(contributing): remove reference to the obsolete chrome extension
docs($routeProvider): fix indentation

Closes #6345

Somebody accidentally padded a list with one-too-many indentations, which caused the actual documentation page to render incorrectly. This should fix it.
chore(doc-app): remove invalid line of code
chore(doc-gen): improve grouping and sorting of api nav items
docs(api): remove ngRoute.$routeParams link from ng section

Closes #6219
chore(doc-gen): add path of project to the doc gen config
docs(modules): remove unused {@installModule} tags
chore(docs): make the layout fully responsive

Closes #6308
chore(package.json): update dgeni dependencies
chore(doc-gen): add formatted error messages to error pages

This got missed in the doc migration: When there is an error in an
Angular app, extra information is placed in the URL, which can be used
by the docs application to display a more useful message.

This fix adds that back in.  The error message templates are extracted
by the minerr tool during build and put into the errors.json file. The
errors-doc processor will load this up and attach these message templates
to the error docs.

The display of these templates was already in place, via the errorDisplay
directive in docs/app/js/errors.js.

(Also, moved the error.template.html file into the angular.js repository
from the dgeni-packages repository as this is specific to the angular.js
project and all the other error related stuff is in here.

Finally, also, added an e2e test that checks that minerr formatted
messages are displayed correctly.

Closes #6363
chore(docs): fix header wrapping for tablet devices
docs(ngMock): document method ngMock.$interval#cancel()

I have been looking around and was not able to find any informations on how to clear the $interval
but reading the source code, sharing is caring!

Closes #6367
docs(core): add note that isObject returns true for arrays

Closes #6353
docs(ie): document IE style attribute interpolation problem

IE has issues with this, it's good to make a note of this.

Closes #6329