Add "start" config option (#165)

Author: ryanwalters

index.d.ts

@@ -10,6 +10,10 @@ declare namespace pathToRegexp {
      * When `true` the regexp allows an optional trailing delimiter to match. (default: `false`)
      */
     strict?: boolean;
+    /**
+     * When `false` the regexp will match the end instead of the entire string. (default: `true`)
+     */
+    start?: boolean;
     /**
      * When `false` the regexp will match the beginning instead of the entire string. (default: `true`)
      */

index.js

@@ -300,11 +300,12 @@ function tokensToRegExp (tokens, keys, options) {
   options = options || {}
 
   var strict = options.strict
+  var start = options.start !== false
   var end = options.end !== false
   var delimiter = escapeString(options.delimiter || DEFAULT_DELIMITER)
   var delimiters = options.delimiters || DEFAULT_DELIMITERS
   var endsWith = [].concat(options.endsWith || []).map(escapeString).concat('$').join('|')
-  var route = ''
+  var route = start ? '^' : ''
   var isEndDelimited = tokens.length === 0
 
   // Iterate over the tokens and create our regexp string.
@@ -342,7 +343,7 @@ function tokensToRegExp (tokens, keys, options) {
     if (!isEndDelimited) route += '(?=' + delimiter + '|' + endsWith + ')'
   }
 
-  return new RegExp('^' + route, flags(options))
+  return new RegExp(route, flags(options))
 }
 
 /**