Fixes Phoenix.Naming.underscore bug #336
Add camelize implementation from mix
Add note to docs about underscore not being the inverse of camelize in
some cases.
Remove failing doctest
Fix Template.UndefiendError exception
Fix Mix.Util references
Merge branch 'pma-master'
Add temporary fix for CodeReloader in test env

`Mix.Task.reenable` cannot be run in the test environment as it causes
subsequent test runs to break on defined module errors for the main
application module. The result requires a complete `rm -rf _build` to fix.

As a temporary fix until a better solution is found, instead of running
the full reenable/recompile mix task for the test env, `IEx.Helpers.r` is
applied to all modules that respond to `phoenix_recompile?`.
This allows files such as Views to be dynamically recompiled for TDD of
views/templates and satisfies the only code reloading required for the test env
today. The dev env code reloading remains unchanged. Close #317