Update: non-option argument instead of --startup-url

[farhadmak]

This pull request should complete #205 , Main updates:

• Removed URL validation to accept links more freely.
• Is able to accept strings to google search. ie. browsh "browsh documentation" will open a google search of the string.

[tombh]

Sorry for the delay. It's been so long since I looked at the code that I can't tell immediately what's going on. Is it easy to add a little test case? Hmm, maybe not, you'd have to do something hacky in this function I think. Anyway, if you think this is good to go, then I'll merge it.

[farhadmak]

I'll look into writing up a test. A few things to note with this code, any argument without a flag will be opened into a new tab. If it is a link, then great, itll open to that link. If not, it does a google search on it. Off the top of your head, does this pose an issue? (i.e another command that has no flag)