Update README.md

To improve the experience for users trying to build ADAM from source, I think it's worth explicitly adding the command to up the PermGen size and to turn off running tests, which should reduce the number of emails to the mailing list about failing builds and allow the new user to get moving with the jar file sooner rather than later.

Feel free to discard if you think either change does more harm than good.
Merge pull request #139 from hammer/patch-1

Update README.md
Update README.md

Change the remote URL to use HTTPS rather than SSH, as [GitHub recommends for users behind a firewall or proxy](https://help.github.com/articles/which-remote-url-should-i-use).
Merge pull request #140 from hammer/patch-2

Update README.md
Changing package declaration to match test file location and removing unused imports and unnecessary semicolons.
Merge pull request #143 from hammerlab/ifq-test-cleanup

Changing package declaration to match test file location and removing unused imports and unnecessary semicolons.
Setup the enforcer plugin
Merge pull request #142 from bigdatagenomics/matt-maven-enforce

Enforce Maven and Java versions
Moving createSparkContext into core

- There are some specific ways that ADAM needs to setup the spark
  context, and can be used if only core is referenced
Updating Changes files
Merge pull request #148 from genomebridge/moveSparkContextCreation

Moving createSparkContext into core