Disable IE Compatibility Mode in docs, examples

...because we don't support it and it may cause problems for people
trying to view the docs in IE.
Alter wording of example Skip Nav link to improve pronunciation

Screen reading applications, including Apple's VoiceOver, improperly pronounce the word "content" in "Skip to content" as an adjective rather than a noun because of insufficient context. "Skip to main content" is pronounced correctly. 

See #6 and Guideline #10 at the following site for more information:
http://redish.net/content/papers/interactions.htmlAlter wording of example Skip Nav link to improve pronunciation
Add note about IE mode tag being included in docs
Merge pull request #10790 from twbs/disable-compatibility-mode

Disable IE Compatibility Mode in docs, examples
Merge pull request #10786 from acspike/skip-nav-link-wording

Alter wording of example Skip Nav link to improve pronunciation
Use "Skip to main content" phrasing consistently; further #10786 fixes
Merge pull request #10796 from twbs/skip-to-main-content

Use "Skip to main content" phrasing consistently; further #10786 fixes
add cross-reference to Input Groups in CSS Form docs; fixes #10792
Merge pull request #10797 from twbs/input-groups-xref

add cross-reference to Input Groups in CSS Form docs; fixes #10792
don't include . in link