some suggestions added to stats and fix a typo in average distance when there are more than one refuel
Merge pull request #61 from pablosca/master

Units view
do not take into account the first refuel for some stats, issue #62 do not fixed correctly
correct fix #62
fixed consumption into refuel form and added distance
fix bug in stats with default car and add ng-if instead of ng-show to All filter option. remove code refuels one car and add a select to refuels list in the same way that it is in stats
fix issue with spentByKilometer and kilometersByLiters Stats. Related with issue #62
added total distance and refuels count into stats
added groups in stats page, also added average capacity by refuel and average spent by refuel
add total to refuel list, fix minor bugs, move add vehicle and add fuel to selects in refuel form
Overview aesthetical changes. General aesthetical changes in buttons. Buttons styles are all the same now
Structure for overview
Fix conflict for overview