Add Circle CI config and remove Travis CI config (#233)

Also update Makefile to build tools locally.
Similar to https://github.com/open-telemetry/rfcs/pull/14.

.circleci/config.yml

@@ -0,0 +1,12 @@
+
+version: 2
+
+jobs:
+  build:
+    docker:
+      - image: circleci/golang:1.12
+    steps:
+      - checkout
+      - run:
+          name: Verify
+          command: make precommit

.gitignore

@@ -21,3 +21,6 @@ bin
 
 # Vim
 .swp
+
+# Misspell binary
+.tools

.travis.yml

@@ -1,17 +0,0 @@
-language: go
-cache:
-  directories:
-    - /home/travis/gopath/pkg/mod
-
-go:
-  - 1.12.x
-
-env:
-  global:
-    GO111MODULE=on
-
-install:
-  - make install-tools
-
-script:
-  - make travis-ci

Makefile

@@ -1,21 +1,20 @@
 # All documents to be used in spell check.
 ALL_DOC := $(shell find . -name '*.md' -type f | sort)
 
-MISSPELL=misspell -error
-MISSPELL_CORRECTION=misspell -w
+TOOLS_DIR := ./.tools
+MISSPELL_BINARY=$(TOOLS_DIR)/misspell
 
-.PHONY: travis-ci
-travis-ci: misspell
+.PHONY: precommit
+precommit: install-misspell misspell
 
-.PHONY: misspell
+ .PHONY: install-misspell
+install-misspell: go.mod go.sum internal/tools.go
+	go build -o $(MISSPELL_BINARY) github.com/client9/misspell/cmd/misspell
+
+ .PHONY: misspell
 misspell:
-	$(MISSPELL) $(ALL_DOC)
+	$(MISSPELL_BINARY) -error $(ALL_DOCS)
 
-.PHONY: misspell-correction
+ .PHONY: misspell-correction
 misspell-correction:
-	$(MISSPELL_CORRECTION) $(ALL_DOC)
-
-.PHONY: install-tools
-install-tools:
-	GO111MODULE=on go install \
-	  github.com/client9/misspell/cmd/misspell
+	$(MISSPELL_BINARY) -w $(ALL_DOCS)