Changed Travis test settings some more to work around API call thrott…

…ling

Test stability

travis update

Changed the tests to be retriable

examples are now export-ignored

added missing docs

users support

test abstraction

 - Added examples for all operations

 - `Alorel\Dropbox\Parameters` now has an `availableSizes()` static method
 - `Alorel\Dropbox\Parameters` now has an `availableFormats()` static method

prep for 0.1