Added helper classes for stream reading and alert creation.

Re: #16
Added try catch to data file write

This should display a dialogue when the data cannot be downloaded.

Also commented out unused code and some minor style changes.

Ref: #16
Minor up of codebase

Ref: #16
Tidy up creation of query xml in helper class

Ref: #16
Added check for timestamp of festival data file.

This allows me to avoid loading the data model if the underlying data
 has not been updated.

This is slightly simplistic, but if intended to avoid a reload of the
 model when there is an error loading the data from the web.

Ref: #16
Added builder object to simplify the display of alert messages.

Ref: #16
Added new helpers to query the underlying android system.

Required the addition of the `ACCESS_NETWORK_STATE` permission to the
 manifest.

Ref: #16
Moved the creation of intent data maps into the `IntentExtras`

Ref: #16
Added dialogue display to main activity to inform user of problems.

This covers:

* Attempting to update when no internet connection is available
* Attempting to display drink data when no festival model is loaded

Ref: #16
Moved tests into directory called `tests`

This means they can be found by the `android-sdk-plugin` default configuration
Corrected typo in ScalaDoc of helper class
Added missing `show()` to the dialogue for missing data model.

Ref: #16
Application now handles the error cases much better

Merge branch 'bugfix/16-HandleErrorsOnDataUpdate' into develop