error in ubuntu install instructions

Could perhaps be expanded with more prose, but this will do for a start.

Used the twice in a row

Also note AWX is named "Tower" now, as we found that simpler.

Fixed double-dash literals. Fixed broken :doc: links. Minor case fixes. Minor wording fixes.

With v1.4.2 setup.py requires httplib2 for install

just darting a mistyped "ansible"

perhaps there may be pip distribution using "pip-install" but "pip install" is universal afaik

  to ansibleworks.com
* Fixed a few misspelled words

Link to the Inventory & Patterns page in places where the Getting
Started guide refer to it, so that users unfamiliar with the
inventory syntax can easily familiarize themselves with it.