Add an advanced text generator based on markov chains.

The advanced text generator's text()-generator is compatible to
Lorem's one and can be used as a drop in replacement.
Fix several issues with markov chain Text provider
Add de_DE locale for Text provider
Fix typo in de_DE/Text locale
Improve documentation of the Text provider
Add Text provider to Factory
Update Text provider with the latest suggestions
Fix tests for Text provider
Merge pull request #254 from TimWolla/advancedTextProvider

Add an advanced text generator based on markov chains.
Refactor and speed up realText formatter bootstrap

With English locale, bootstrap of realText passes from 5s to under 100ms
Merge pull request #263 from fzaninotto/faster_realText

Refactor and speed up realText formatter bootstrap
Revert test file modified by mistake
Add French realText provider

Also, fixed an utf8 bug in realText provider
Merge pull request #264 from fzaninotto/french_realText

Add French realText provider
Fix PHP 5.3 compatibility
Limit Markov chain order to 5

Higher orders produce about the same randomness.
Fix realText order limit
add Faker\Provider\Base::randomElements
optimize randomElements performance
make randomElements ~12% faster