Reduce runtime

[lverns]

When checking for updates, particularly on large projects with many top-level dependencies, and several repositories, the majority of the runtime is spent querying remote servers for version information. By running these queries in parallel we make checking for updates a lot faster.

Caveats:

• ~I've not tested this with git dependencies, but I'm assuming those checks are also threadsafe~ Reading the code, it looks threadsafe to me. Also, testing on the test alias in the project gives the same results for olical/cljs-test-runner before and after the change.
• ~Since the code for --update uses a different and more complex looping mechanism, it does not receive any speed improvements from this change.~ Pushed commits expanding the speed up to the --update code as well.

[Olical]

Damn this is really cool, thank you very much! I've looked over the commits and am happy, will just give it a test locally before merging, great work! :clap:

[Olical]

Excellent, no difference other than much faster. Great work, thank you very much!