fixes #677 - mistype in docs/quickstart
Flash messages signals

If we send a signal when a template is rendered why not when a message
is flashed? One real world use case is in tests, this signal should make
flash messages expectation easier to implement.
Merge pull request #681 from dmizelle/docs-quickstart

fixes #677 - mistype in docs/quickstart
fix typo in quickstart guide
Added more information about app factories.
Merge pull request #693 from untitaker/factory_docs

Added more information about app factories.
Merge pull request #692 from mikegagnon/patch-1

fix typo in quickstart guide
Merge pull request #687 from poiati/flash-signal

Flash messages signals
Documented new signal message_flashed
Added signal for registration of blueprints

Fix #691