phpenv-hooks accept 2nd argument.

Let phpenv-hooks accept a second argument the hook name.
phpenv-hooks execute hook script.

If hook was passed to phpenv-hooks and the file is executable then execute it.
Implement sample install hooks.

For POC added 2 common hook implementations to phpenv-install
pre-configure called before executing ./configure.
post-configure called if ./configure succeeded.
Stubbed hook scripts.

2 stubbed script files to serve as placeholders for the 2 implementaed hooks.
Add igbinary extension
Added xdebug extension
Added uri-tomplate extension
Added apc extension
Added memcached extension
Added http extension
Added ncurses extension
Add phalcon extension
Added yaf extension
phpenv shell improve output --unset

let unset inform you about the changes
phpenv shell more robust and improved output

Decrease possibility of failure and increase verbosity by displaying the changed version without having to call shell --version
phpenv shell fix bug with echo response

This fixes the bug where php shell would respond with echo by just echoing the information. This is now reusable and the same routines for output is called by any change
Code conventions

We add "function" to functions
Always output application name and version

Single point forl displaying app name and version to always be prompted.
For most cases anyway as this is not practical due to scripts calling each other so this might require more tweaking still.
Remove redundant appname display

Removed the app name display from help as it is now displayed by default.
Code convention

Consistently prefix functions with functions.