Allow search() function to use params parameter
Allow search() function to use params parameter

As shown in [this comment](https://www.reddit.com/r/NoStupidQuestions/comments/3dtjbs/how_do_you_stick_photos_together/) by [/u/GoldenSights](http://www.reddit.com/u/GoldenSights), this allows the params parameter within the search() function to be altered. This allows for greater use of the function, from defining pages via `params={'after' : 't3_code'}` to the option of specifically defining to use the "new" legacy search e.g. `params={'feature' : 'legacy_search'}`
gschizas/praw,darthkedrik/praw,13steinj/praw,darthkedrik/praw,gschizas/praw,leviroth/praw,RGood/praw,RGood/praw,praw-dev/praw,praw-dev/praw,nmtake/praw,13steinj/praw,nmtake/praw,leviroth/praw