Use project to build Documenter docs (JuliaLang#480)

* Use project to build Documenter docs

This should also fix building the docs, which haven't been deployed for one year.

* Fix

.travis.yml

@@ -17,4 +17,14 @@ git:
 #  - julia -e 'Pkg.clone(pwd()); Pkg.build("StatsBase"); Pkg.test("StatsBase"; coverage=true)'
 after_success:
   - julia -e 'using Pkg; Pkg.add("Coverage"); using Coverage; Coveralls.submit(process_folder()); Codecov.submit(process_folder())';
-  - julia -e 'using Pkg; Pkg.add("Documenter"); include(joinpath("docs", "make.jl"))'
+jobs:
+  include:
+    - stage: "Documentation"
+      julia: 1.0
+      os: linux
+      script:
+        - julia --project=docs/ -e 'using Pkg; Pkg.develop(PackageSpec(path=pwd()));
+                                    Pkg.instantiate()'
+        - julia --project=docs/ docs/make.jl
+      after_success: skip
+

docs/Project.toml

@@ -0,0 +1,5 @@
+[deps]
+Documenter = "e30172f5-a6a5-5a46-863b-614d45cd2de4"
+
+[compat]
+Documenter = "~0.22"

docs/make.jl

@@ -1,7 +1,11 @@
 using Documenter, StatsBase, Statistics, Random
 
+# Workaround for JuliaLang/julia/pull/28625
+if Base.HOME_PROJECT[] !== nothing
+    Base.HOME_PROJECT[] = abspath(Base.HOME_PROJECT[])
+end
+
 makedocs(
-    format = :html,
     sitename = "StatsBase.jl",
     modules = [StatsBase],
     pages = ["index.md",
@@ -23,9 +27,5 @@ makedocs(
 )
 
 deploydocs(
-    repo = "github.com/JuliaStats/StatsBase.jl.git",
-    target = "build",
-    julia  = "1.0",
-    deps   = nothing,
-    make   = nothing
-)
+    repo = "github.com/JuliaStats/StatsBase.jl.git"
+)