Add FreeBSD 10 support.

This was reported to work by @bthomson in #71.
Closes #71.
Improve documentation style slightly.

Use more idiomatic style for comments, which includes a space after the
//. See
https://code.google.com/p/go-wiki/wiki/CodeReviewComments#Comment_Senten
ces.
Remove references to LockOSThread Wiki example; simply mention
runtime.LockOSThread() in README instead.
Other than docs, there are no code or behavior changes.
Merge pull request #72 from go-gl/feature/freebsd-support

Add FreeBSD 10 support.
Modify README to note runtime.LockOSThread() is needed.

Fix missing runtime.LockOSThread() in example code.
Merge pull request #73 from go-gl/improve-documentation-style

Improve documentation style slightly.
Merge branch 'master' into devel_glfw3.1