cljr-replace-use now handles clauses with :only

Additionally, cljr-refactor-use also sorts the ns if auto-sort-ns is t.

Support for :exclude is left as an exercise for the reader.

Closes #31
Update travis to use EVM

See #29
Add the gnu mirror as package source for Cask
Remove mention of emacs 23.4 from travis build file
add cljr-move-defn

The following features have been implemented:

- Move the defn containing POINT to a new ns.
- Move the defns selected by the region to a new ns.
- Fail if the selection is deemed to be unbalanced by paredit and make
  sure we don't create whitespace errors in either buffers
- New home is found using find-file prompt.
- The defns are referred into the ns from which they were moved.
- Private functions, created with defn-, are not referred after moving.

Known limitations:

- The ns we're moving functions into can be left in an inconsistent
because no analysis is done to :require or :refer dependencies.
Merge pull request #29 from expez/move-var

Refactoring to move forms