Add dependency on macro paradise only when Scala 2.10 is used
Add dependency on macro paradise only when Scala 2.10 is used

Spire uses macro paradise plugin just for quasiquotes. Quasiquotes got
merged into Scal reflection in Scala 2.11 so there's no need to depend on
the macro paradise plugin in case Scala 2.11 is used.

This commit makes inclusion of the plugin conditional on the Scala version
used in the build.

AlecZorab/spire,codeaudit/spire,rklaehn/spire,tixxit/spire,woparry/spire,adampingel/spire,AlecZorab/spire,rklaehn/spire,non/spire,codeaudit/spire,JackSullivan/spire,kevinmeredith/spire,guersam/spire,siddhartha-gadgil/spire,adampingel/spire,siddhartha-gadgil/spire,woparry/spire,JackSullivan/spire,tixxit/spire,non/spire,kevinmeredith/spire,guersam/spire