Why bottle you may ask? One of the keys to a great mid with Razor is having complete rune control. With bottle early you can afford to be super aggressive, and come level 6 you make an awesome ganker. Make sure to tell your support to ward one of the runes for you if he doesn't.
You must play aggressive if you go mid. Razor is great at harassing if you can land your q right at the tip. Don't waste your mana on it until level three however. The first level of damage isn't worth it.
A great way to help yourself farm and harass is if you can link yourself with the other mid withough taking much dmg. You can easily 1v1 at almost any level due to your AD drain and regen with bottle. Hit him with a q as he runs to add insult to injury.
You should have at least lvl 1 boots by the time you hit lvl 6 and with correct rune control should easily be at full hp and mana most of the game. As soon as you hit 6, go for the rune as it spawns and gank wherever you go to get the rune.
Tell your team to let them push as much as they can and deny creeps or pull the lane so they have to over-extend.
As soon as the enemies creep wave is about to die, or if they go to far, activate your ult and Q/W with full mana it should be fine. They probably won't have boots so you can easily catch up with them. By the time they get back to turret you might even be able to add in another q. Don't forget to use bottle while not taking damage. With a little help this should be an easy double kill.
A little later in the game the rushed Sange will slow them even more making kills that much easier.
Late Game / Team Fights
After you have boots fully built you can either go Ogre Club or rush a defensive item depending on their team build up.
Always build at least one defensive item after boots. If they are heavy on magic dmg you can go straight for ogre and rush a BkB. If it is hard for you to farm just build a cloak before Ogre Club.
Whether they are heavy on attack dmg or not Vanguard isn't the greatest item for you. It has a much too high price for only a 20 damage block. A better item would be Plate mail for your Assault Cuirass later.
After you have your defensive item and Sange you should be able to stay alive fairly easily. You can either finish off Sange and Yasha for some extra speed, or a Desolater for a much higher damage output with some less maneuverability. I personally prefer Sanga and Yasha first. If you are getting very fed, however, Eye of Skadi works extremely well.
End game you can always build a Aghanim's Scepter for some extra push and team fighting capabilities. Or some extra defense if they start focusing you.
Pros and Cons with this build
This build is focused at carrying your team to victory and not so much at staying in the background being a support carry or 'anti-carry'. You shouldn't be too squishy with Power Treads early off but your damage will lack just slightly. Your W more than makes up for the lack in damage however, and with an early Sange you will be even tankier and have more damage/ a slow.
Mid - end game Razor will demolish the other team. With this build you will be very hard to kill, you should be well farmed with bottle mid, and you will deal out massive damage with your W and item build.
Early game it is harder for you to last hit with your low attack damage. You can use your Q to harass with and at the same time get an extra few creeps. WIf you play smart and are aggressive however you can get the other guy off your *** a bit though.
If you are doing well mid-end game the whole other team will focus you, and Razor lacks escapability. This is why defense is extremely important. Your team must be able to peel people off of you if you are getting hit too hard.