Fix style problems (#290)

.github/ISSUE_TEMPLATE.md

 ### What version of pprof are you using?
 
 If you are using pprof via `go tool pprof`, what's your `go env` output?
-If you run pprof from Github, what's the Git revision?
+If you run pprof from GitHub, what's the Git revision?
 
 
 ### What operating system and processor architecture are you using?

CONTRIBUTING.md

 git push aalexand
 ```
 
-where `aalexand` is your Github user ID. Then proceed to the Github UI to send a
+where `aalexand` is your GitHub user ID. Then proceed to the GitHub UI to send a
 code review.
 
 # Code reviews
 
 All submissions, including submissions by project members, require review.
-We use Github pull requests for this purpose.
+We use GitHub pull requests for this purpose.
 
 The pprof source code is in Go with a bit of JavaScript, CSS and HTML. If you
 are new to Go, read [Effective Go](https://golang.org/doc/effective_go.html) and

internal/driver/webhtml.go

 package driver
 
 import "html/template"
+
 import "github.com/google/pprof/third_party/d3"
 import "github.com/google/pprof/third_party/d3tip"
 import "github.com/google/pprof/third_party/d3flamegraph"