Fix depwarns for Julia 1.0 (#12)

* fix depwarns

* use isempty

* updates

Author: abhijithch

.travis.yml

@@ -4,8 +4,9 @@ os:
 #  - osx
 julia:
   - 0.6
+  - 0.7
   - nightly
 notifications:
   email: false
 after_success:
-  - julia -e 'cd(Pkg.dir("Showoff")); Pkg.add("Coverage"); using Coverage; Coveralls.submit(Coveralls.process_folder())';
+  - julia -e 'using Pkg; cd(Pkg.dir("Showoff")); Pkg.add("Coverage"); using Coverage; Coveralls.submit(Coveralls.process_folder())';

src/Showoff.jl

@@ -35,7 +35,7 @@ end
 # Floating-point
 
 function concrete_minimum(xs)
-    if done(xs, start(xs))
+    if isempty(xs)
         throw(ArgumentError("argument must not be empty"))
     end
 
@@ -57,7 +57,7 @@ end
 
 
 function concrete_maximum(xs)
-    if done(xs, start(xs))
+    if isempty(xs)
         throw(ArgumentError("argument must not be empty"))
     end