Improve the Clojure Package README to Make it Easier to Get Started (a…

…pache#12881)

* Improve the README and make it easier to get started

* Implement feedback from @ChaiBapchya and @daveliepmann

* combined deps

* Add wget

Co-Authored-By: gigasquid <[email protected]>

* WIP: update readme

* WIP: readme option 3

* Add section links to Clojure README

Link each install option with the corresponding README section
containing instructions for that option.

An existing link to Maven search is removed because it interferes with
the section links and it is replicated in the Option 1 instructions
below.

Per my PR suggestion:
https://github.com/apache/incubator-mxnet/pull/12881/files/22bbe55d8d62be9ff3aebf693f73fa6049afc01d#r226822148

* fix typo

Co-Authored-By: gigasquid <[email protected]>

* fix formatting

Co-Authored-By: gigasquid <[email protected]>

* fix formatting

Co-Authored-By: gigasquid <[email protected]>

* fix link

Co-Authored-By: gigasquid <[email protected]>

* Some more updates for the Clojure README