Added htop to `system_packages` in common role

Fixes #15
Fixed wp-config salts replacement

* Regexp now properly handles newlines (since javascript doesn't match them with dots)
* Separate literal string replace (as split(match).join(replace)) since generated salts could contain "$" strings interpreted as backrefs
Merge pull request #51 from genesis/generator-wpconfig-salts-fix

[Generator] Fixed wp-config salts replacement
Generator will now remove + replace existing blocks from README and htaccess; also added genesis version to README
Run vagrant up prior to up:db & down:db
Find existing and prompt for wordpress table prefix

Fixes #43
Added `iftop` for network bandwidth usage
Calculating php memory_limit and apache prefork directives; allowing manual overrides as global vars

* if no manual override, calculating php memory_limit via `shell` task
* replacing apache default prefork config with include to separate file
* generating prefork.conf from template (incl calculated directive values)
* using custom `replace` module, see ansible/ansible#4889

Fixes #56
Replaced bash psuedo-ternary with jinja inline conditional
Switched to manual overrides grouped into sections; removed conflicting settings from roles/wordpress/vars

Note that template logic in prefork.conf is necessarily more complex (as we cannot assign to dicts), but also somewhat more explicit and less magical. I'm okay with this.
Added natdnshostresolver customization for virtualbox

Props to @weeirishman for finding this! See http://www.virtualbox.org/manual/ch09.html#nat_host_resolver_proxy
Ensuring port has no leading zero by removing all zeroes

Fixes #49
Fixed issue where php_settings, reserved_memory, or apache_settings are not defined
Removed outdated var names from common/vars/main
Merge pull request #64 from genesis/56-apache-php-tuning

Apache + PHP performance tuning
Bump to v0.2.29
Merge branch 'master' of github.com:genesis/wordpress
Merge pull request #66 from genesis/49-ssh-port-octet

Ensuring ssh port isn't an octet
Merge pull request #65 from genesis/vagrant-natdnshostresolver

Vagrant/Virtualbox - Using host resolver as a DNS proxy
Merge pull request #59 from genesis/5-DB-tasks

Run vagrant up prior to up:db & down:db