Depend on underscore>= 1.6.0

Fixes #161
v0.7.1
Updates Underscore dependency in bower.json
v0.7.2
Update CHANGELOG.md
Delete backbone.radio.min.map
Adds extra arguments to methods.
Update DEBUG logging behavior in remove methods
Add overwrite debug warning for commands and requests
Uses rest instead of slice.
v0.8.0
Fixes a bug where stopReplying and stopComplying would unregister the wrong events.
v0.8.1
Remove use of _.constant to support underscore@1.4.4 #163
v0.8.2
Use switch args in top-level api for perf