Makes Julia 1.1 the minimum supported version

The dependency PlanarConvexHulls.jl requires Julia 1.1 or greater. See tkoolen/PlanarConvexHulls.jl#2

Author: zygmuntszpak

.appveyor.yml

@@ -1,8 +1,8 @@
 # Documentation: https://github.com/JuliaCI/Appveyor.jl
 environment:
   matrix:
-  - julia_version: 0.7
-  - julia_version: 1.0.3
+  - julia_version: 1.1
+  - julia_version: 1.2
   - julia_version: nightly
 platform:
   - x86

.travis.yml

@@ -4,7 +4,8 @@ os:
   - linux
   - osx
 julia:
-  - 1.0
+  - 1.1
+  - 1.2
   - nightly
 matrix:
   allow_failures:

Project.toml

@@ -26,7 +26,7 @@ ImageCore = ">= 0.8.3"
 PlanarConvexHulls = ">= 0.3.0"
 StaticArrays = ">= 0.11.1"
 OffsetArrays = ">= 0.11.1"
-julia = "^1"
+julia = ">= 1.1"
 
 [extras]
 ImageCore = "a09fc81d-aa75-5fe9-8630-4744c3626534"