use table to dispaly dhcp lease & minor fix (dhcp)

Hi xtr4nge,

I did some small fix to dhcp lease and add a feature to display dhcp lease in html ```<table>```, as well as highlight the currently online dhcp clients. The preview of this feature is the following:
![default](https://cloud.githubusercontent.com/assets/1560135/4640510/c84b977a-5422-11e4-8244-0e13da5b4efb.PNG)