Fixed whitespace
Do not create an application object unless required.
No fiddling with configuration settings from within a library.

We really do not have any business touching these; we'll just keep
display_errors as is, do not attempt to change the error_reporting
state, and raise a notice instead of brute-forcing the configuration
when we detect to be under the minimum memory limit.
switch/case fallthrough is bad mkay?
Minor: documentation / whitespace
Keep the $application around for future calls to run().
Refactoring:

- removed side effects from constructor
- factored out memory check
- added error checking to PHAR download and install
- trigger PHAR download only when required (lazy-load)