Remove extra-lint

- standard enforces 'let' and 'const' now
- I've never been a fan of the <100 chars per line rule since it violates the standard philosophy. it should be possible to write conformant code without needing a tool, so 'magic numbers' like 'no more than X lines/chars/statements' are not ideal

bin/extra-lint.js

@@ -1,39 +0,0 @@
-#!/usr/bin/env node
-
-const walkSync = require('walk-sync')
-const fs = require('fs')
-const path = require('path')
-
-let hasErrors = false
-
-// Find all Javascript source files
-const files = walkSync('src', { globs: ['**/*.js'] })
-console.log('Running extra-lint on ' + files.length + ' files...')
-
-// Read each file, line by line
-files.forEach(function (file) {
-  const filepath = path.join('src', file)
-  const lines = fs.readFileSync(filepath, 'utf8').split('\n')
-
-  lines.forEach(function (line, i) {
-    let error
-
-    // No lines over 100 characters
-    if (line.length > 100) {
-      error = 'Line >100 chars'
-    }
-
-    if (line.match(/^var /) || line.match(/ var /)) {
-      error = 'Use const or let'
-    }
-
-    if (error) {
-      const name = path.basename(file)
-      console.log('%s:%d - %s:\n%s', name, i + 1, error, line)
-      hasErrors = true
-    }
-  })
-})
-
-if (hasErrors) process.exit(1)
-else console.log('Looks good!')