Polish docs

Hi,

while browsing on hackage I noticed some small issues and went ahead to fix them.
Detailed listing:

- put qualified imports into code formatting
- remove `Debug.Trace` import
- varadic -> variadic
- varaibles -> variables
- enviorment -> environment
- replace *one* with __one__ to make it bold
- Remove redundant `($)`

[![24pullrequests](http://24pullrequests.com/assets/logo-625222452ffc0d57272decb6f851a7fe.png)](http://24pullrequests.com)

Best,
Markus