Fix the build system

src/cakefile.coffee

@@ -8,7 +8,7 @@ option "-m", "--map", "Whether to generate source maps."
 
 task "build", "Builds the project.", (options) ->
 	sourcemaps = if options.map then ["--map"] else []
-	run "coffee", "--compile", sourcemaps..., "--no-header", "--output", "lib", "src"
+	npx "coffee", "--compile", sourcemaps..., "--no-header", "--output", "lib", "src"
 
 task "clean", "Deletes all generated files.", ->
 	rmSync join("lib", file) for file from readdirSync "lib" when not file.endsWith ".d.ts"
@@ -29,7 +29,7 @@ task "publish", "Publishes the package.", ->
 
 task "test", "Runs the test suite.", ->
 	env.NODE_ENV = "test"
-	run "coffee", "--compile", "--map", "--no-header", "--output", "lib", "src", "test"
+	npx "coffee", "--compile", "--map", "--no-header", "--output", "lib", "src", "test"
 	run "node", "--enable-source-maps", "--test", "--test-reporter=spec", "lib/**/*_test.js"
 
 task "version", "Updates the version number in the sources.", ->
@@ -38,7 +38,7 @@ task "version", "Updates the version number in the sources.", ->
 
 task "watch", "Watches for file changes.", (options) ->
 	sourcemaps = if options.map then ["--map"] else []
-	run "coffee", "--compile", sourcemaps..., "--no-header", "--output", "lib", "--watch", "src", "test"
+	npx "coffee", "--compile", sourcemaps..., "--no-header", "--output", "lib", "--watch", "src", "test"
 
 # Executes a command from a local package.
 npx = (command, args...) -> run "npm", "exec", "--", command, args...