FIX: remove php 5 support claim from ReadMe

[TeaObvious]

Yesterday i was bound 2 hours to find why i am hitting this issue: #204

The reason is, that TasmoAdmin does not like php5 - at least not the version 5.4.16 delivered with CentOS. Once i installed a php7 this error vanished immediately and TasmoAdmin worked like charm. Switching back and forth between php5 and php7 and the error returns/vanishes reproducible.

I recommand so simply remove the php5 part of this ReadMe Line "php7 recommended (works with php5 too)" to prevent any further confusion.

While changing the ReadMe you could also add these 3 lines to show how to enable SELinux support.

semanage fcontext -a -t httpd_sys_rw_content_t "/var/www/tasmoadmin/tasmoadmin/data(/.*)?"
semanage fcontext -a -t httpd_sys_rw_content_t "/var/www/tasmoadmin/tasmoadmin/tmp(/.*)?"

followed by a

restorecon -Rv /var/www/