Update doc building

.travis.yml

@@ -30,5 +30,13 @@ script:
 after_success:
   - julia -e 'cd(Pkg.dir("VegaLite")); Pkg.add("Coverage"); using Coverage; Codecov.submit(Codecov.process_folder())'
   - julia -e 'cd(Pkg.dir("VegaLite")); Pkg.add("Coverage"); using Coverage; Coveralls.submit(Coveralls.process_folder())'
-  - julia -e 'ps=Pkg.PackageSpec(name="Documenter", version="0.19"); Pkg.add(ps); Pkg.pin(ps)'
-  - julia -e 'cd(Pkg.dir("VegaLite")); include(joinpath("docs", "make.jl"))'
+
+jobs:
+  include:
+    - stage: "Documentation"
+      julia: 1.0
+      os: linux
+      script:
+        - julia --project=docs/ -e 'using Pkg; Pkg.instantiate(); Pkg.develop(PackageSpec(path=pwd()))'
+        - julia --project=docs/ --color=yes docs/make.jl
+      after_success: skip

docs/Project.toml

@@ -0,0 +1,8 @@
+[deps]
+DataFrames = "a93c6f00-e57d-5684-b7b6-d8193f3e46c0"
+Documenter = "e30172f5-a6a5-5a46-863b-614d45cd2de4"
+Query = "1a8c2f83-1ff3-5112-b086-8aa67b057ba1"
+VegaDatasets = "0ae4a718-28b7-58ec-9efb-cded64d6d5b4"
+
+[compat]
+Documenter = "~0.20"

docs/make.jl

@@ -1,14 +1,7 @@
 using Documenter, VegaLite
 
-info("Building docs...")
-
-Pkg.add("DataFrames")
-Pkg.add("VegaDatasets")
-Pkg.add("Query")
-
 makedocs(
   modules=[VegaLite],
-  format=:html,
   sitename = "VegaLite.jl",
   pages = [
     "Home" => "index.md",
@@ -47,9 +40,5 @@ makedocs(
 )
 
 deploydocs(
-    deps = nothing,
-    make = nothing,
-    target = "build",
     repo = "github.com/fredo-dedup/VegaLite.jl.git",
-    julia = "1.0"
 )