Improve page loading time for the Protips page #371

Adding eager loading of Protip search results to minimize the number of sql queries during page rendering.

Some mini-profiler data:
Profiling Before
```
GET http://localhost:3000/	1469.5	2881.1	+0.0	1 sql	0.4
  Executing action: index	67.7	1411.6	+1468.0	13 sql	7.7
   Net::HTTP POST /track/	97.8	97.8	+1500.0	
   Net::HTTP GET /opportunities/opportunity/_sea...	2.1	2.1	+1605.0	
   Rendering: protips/index	40.8	1116.0	+1631.0	7 sql	4.5
    Rendering: protips/_grid	380.7	1075.2	+1672.0	44 sql	19.0
     Rendering: protips/_mini	45.0	45.0	+1701.0	8 sql	5.7
     Rendering: protips/_mini	27.5	27.5	+1769.0	6 sql	3.3
     Rendering: protips/_mini	27.0	27.0	+1816.0	5 sql	2.8
     Rendering: protips/_mini	28.4	28.4	+1862.0	5 sql	2.5
     Rendering: protips/_mini	25.4	25.4	+1917.0	5 sql	2.8
     Rendering: protips/_mini	105.8	105.8	+1965.0	5 sql	2.7
     Rendering: protips/_mini	35.0	35.0	+2088.0	5 sql	2.9
     Rendering: protips/_mini	24.8	24.8	+2148.0	5 sql	2.5
     Rendering: protips/_mini	28.7	28.7	+2189.0	5 sql	2.8
     Rendering: protips/_mini	25.5	25.5	+2235.0	5 sql	3.0
     Rendering: protips/_mini	25.3	25.3	+2277.0	5 sql	2.5
     Rendering: protips/_mini	25.3	25.3	+2320.0	5 sql	2.3
     Rendering: protips/_mini	23.9	23.9	+2366.0	5 sql	2.4
     Rendering: protips/_mini	32.2	32.2	+2410.0	5 sql	2.6
     Rendering: protips/_mini	33.0	33.0	+2461.0	5 sql	2.6
     Rendering: protips/_mini	33.0	33.0	+2513.0	5 sql	2.6
     Rendering: protips/_mini	107.2	107.2	+2572.0	5 sql	4.6
     Rendering: protips/_mini	41.4	41.4	+2705.0	5 sql	5.2
   Rendering: layouts/application	71.9	128.1	+2747.0	
    Rendering: application/_nav_bar	20.0	21.2	+2781.0	
    Rendering: shared/_footer	12.8	34.6	+2828.0	
     Rendering: shared/_mixpanel_properties	21.8	21.8	+2841.0	7 sql	3.7
 ```    
Profiling After
```
GET http://localhost:3000/	1471.6	2350.0	+0.0	1 sql	0.4
  Executing action: index	117.2	878.4	+1471.0	20 sql	17.0
   Net::HTTP POST /track/	108.3	108.3	+1505.0	
   Net::HTTP GET /opportunities/opportunity/_sea...	2.7	2.7	+1667.0	
   Rendering: protips/index	35.2	527.4	+1695.0	7 sql	4.3
    Rendering: protips/_grid	237.0	492.1	+1730.0	
     Rendering: protips/_mini	19.8	19.8	+1741.0	2 sql	1.3
     Rendering: protips/_mini	10.3	10.3	+1772.0	1 sql	0.6
     Rendering: protips/_mini	7.4	7.4	+1802.0	
     Rendering: protips/_mini	8.0	8.0	+1825.0	
     Rendering: protips/_mini	8.1	8.1	+1844.0	
     Rendering: protips/_mini	16.9	16.9	+1865.0	
     Rendering: protips/_mini	8.0	8.0	+1897.0	
     Rendering: protips/_mini	9.0	9.0	+1918.0	
     Rendering: protips/_mini	62.6	62.6	+1939.0	
     Rendering: protips/_mini	15.7	15.7	+2013.0	
     Rendering: protips/_mini	10.1	10.1	+2046.0	
     Rendering: protips/_mini	8.9	8.9	+2073.0	
     Rendering: protips/_mini	8.4	8.4	+2093.0	
     Rendering: protips/_mini	12.7	12.7	+2113.0	
     Rendering: protips/_mini	12.0	12.0	+2137.0	
     Rendering: protips/_mini	12.1	12.1	+2160.0	
     Rendering: protips/_mini	12.9	12.9	+2184.0	
     Rendering: protips/_mini	12.4	12.4	+2209.0	
   Rendering: layouts/application	69.8	122.9	+2222.0	
    Rendering: application/_nav_bar	18.5	19.3	+2258.0	
    Rendering: shared/_footer	13.2	33.1	+2301.0	
     Rendering: shared/_mixpanel_properties	19.9	19.9	+2313.0	7 sql	3.7
    Rendering: shared/_footer	19.9	47.7	+2439.0	
     Rendering: shared/_mixpanel_properties	27.7	27.7	+2459.0	7 sql	3.8
```