v2.1.0 Release

- [ ] ~~#52 Add search feature~~
- [x] #55 Remove message title from the subnav
- [ ] ~~#77 Message Series page enhancements~~
- [x] #95 Browse messages by book
- [x] #96 Browse messages by teaching series
- [ ] ~~#97 Browse messages by date~~
- [ ] ~~#80 Social media links~~
- [x] #112 Image overlap in Newsletters
- [x] Drupal updates:
    - [x] Drupal core 7.34
    - [x] Chaos tool suite (ctools) 7.x-1.5
    - [x] Google Analytics 7.x-2.1
    - [x] Webform 7.x-4.2
    - [x] XML sitemap 7.x-2.1