Update Twitter/Facebook exercise description (#202)

README.md

@@ -289,7 +289,7 @@ Check out the following links to get a better idea of what to expect:
 | Question | |
 |---|---|
 | Design Pastebin.com (or Bit.ly) | [Solution](solutions/system_design/pastebin/README.md) |
-| Design the Twitter timeline (or Facebook feed)<br/>Design Twitter search (or Facebook search) | [Solution](solutions/system_design/twitter/README.md) |
+| Design the Twitter timeline and search (or Facebook feed and search) | [Solution](solutions/system_design/twitter/README.md) |
 | Design a web crawler | [Solution](solutions/system_design/web_crawler/README.md) |
 | Design Mint.com | [Solution](solutions/system_design/mint/README.md) |
 | Design the data structures for a social network | [Solution](solutions/system_design/social_graph/README.md) |