Test qaoa

[yzchen-phy]

Separate graph generation and MaxCut Hamiltonian generation to be more flexible. Can use Graphs.jl package to generate the graph for MaxCut.
Put ADAPT-QAOA types of pools (including the standard QAOA mixer) under ADAPT-QAOA module.

[kmsherbertvt]

@yzchen-phy Please consider the following changes before I accept the pull request:

1. We need only have the one example script for qaoa; please replace test/maxcut_qaoa.jl with your test/maxcut_qaoa1.jl. (Different methods to accomplish things can be included as comments.)

2. Add new modules you've defined (even if they are sub-modules) to the docs/src/index.mdfile.

3. Avoid using packages, or if you do, please explicitly wrap the file into its own module, to contain the bloated namespace.

[kmsherbertvt]

Add an s

(I am just exploring the interface here, don't mind me. I'm guessing this comment is going to have some link to the actual line of code?)

[kmsherbertvt]

I do seem to have found a spot in the interface which lets me "edit" the file, but it seems to actually be on Yanzhu's fork (which makes sense), and I'm guessing Yanzhu would have had to approve the change for it to actually be committed... We can try it out next time. :)