Sandbox autoconf213 to prevent conflicts

Fixes a race condition where autoconf 2.13 may be installed prior to autoconf 2.69+
and end up linked into the main homebrew folder causing homebrew to throw errors
when installing the later non sandboxed version
[FEATURE] Increase various .ini resource refaults and improve XDebug config
[BUGFIX] Update spec fixtures for recent changes
Merge pull request #39 from castiron/gb/better-dev-defaults

Make .ini defaults a little bit more forgiving
Add PHP 5.4.27, 5.4.28. 5.4.29, 5.5.11, 5.5.12, 5.5.13
Fixes syntax and specs
Merge pull request #41 from webflo/new-versions

Add PHP 5.4.27, 5.4.28. 5.4.29, 5.5.11, 5.5.12, 5.5.13
Merge pull request #40 from webflo/xhprof

Add Xhprof extension.
Issue #42: Fix compiling of recent php versions
Fix php_spec
Merge pull request #43 from webflo/fix-compile

Issue #42: Fix compiling of recent php versions
Set pecl to be the default on darwin
Merge pull request #36 from boxen/fix-sandboxing

Fix autoconf 2.13 sandboxing
[BUGFIX] pm.max_children too small for some (XHR-heavy) projects
Merge pull request #47 from castiron/gb/max-children

[BUGFIX] pm.max_children too small for some (XHR-heavy) projects
Merge pull request #45 from boxen/fixproviders

Set PECL to be the default extension provider
Merge boxen/master