Using compile-mode in cljsbuild-mode.

Marking errors and warnings and linking to source.
Reading compilation command from the minibuffer.
Provided most common build commands in minibuffer history.
Merge branch 'pwojnowski-master'
update usage instructions README
Redefined "g" key to run cljsbuild-start.
Merge pull request #6 from pwojnowski/master

Redefined "g" key to run cljsbuild-start.