Change serveradmin default to undef

`serveradmin` is expecting a string, but defaults to `false`. It should
be `undef` to match all the other string parameter defaults.
Release 0.11.0

Summary:

This release adds preliminary support for Windows compatibility and multiple rewrite support.

Backwards-incompatible Changes:

- The rewrite_rule parameter is deprecated in favor of the new rewrite parameter
  and will be removed in a future release.

Features:

- add Match directive
- quote paths for windows compatibility
- add auth_group_file option to README.md
- allow AuthGroupFile directive for vhosts
- Support Header directives in vhost context
- Don't purge mods-available dir when separate enable dir is used
- Fix the servername used in log file name
- Added support for mod_include
- Remove index parameters.
- Support environment variable control for CustomLog
- added redirectmatch support
- Setting up the ability to do multiple rewrites and conditions.
- Convert spec tests to beaker.
- Support php_admin_(flag|value)s

Bugfixes:

- directories are either a Hash or an Array of Hashes
- Configure Passenger in separate .conf file on RH so PassengerRoot isn't lost
- (docs) Update list of `apache::mod::[name]` classes
- (docs) Fix apache::namevirtualhost example call style
- Fix $ports_file reference in apache::listen.
- Fix $ports_file reference in Namevirtualhost.
Fix typos in templates/vhost/_itk.erb

Basically, this wouldn't have worked because of mass typos. FTFY
Merge pull request #599 from hunner/serveradmin_default

Change serveradmin default to undef
Merge pull request #601 from hunner/fix_itk

Fix typos in templates/vhost/_itk.erb
Merge pull request #600 from blkperl/release_011

Release 0.11.0 NOW do README stuff later as bugfix
Fix typo in mod passenger documentation

The rails_auto_detect and rack_auto_detect should not have an underscore between auto and detect.
Merge pull request #611 from ubergeek42/patch-1

Fix typo in mod passenger documentation