Add --summary-only flag

[Goooler]

Tested it manually.

./diffuse diff --summary-only /Users/goooler/Downloads/Lawnicons.2.17.0.apk /Users/goooler/Downloads/Lawnicons.2.17.1.apk
OLD: Lawnicons.2.17.0.apk (signature: V2)
NEW: Lawnicons.2.17.1.apk (signature: V2)

          │            compressed             │            uncompressed            
          ├───────────┬───────────┬───────────┼───────────┬───────────┬────────────
 APK      │ old       │ new       │ diff      │ old       │ new       │ diff       
──────────┼───────────┼───────────┼───────────┼───────────┼───────────┼────────────
      dex │   1.6 MiB │   1.6 MiB │    +171 B │   3.2 MiB │   3.2 MiB │     +760 B 
     arsc │   1.8 MiB │   1.8 MiB │  +8.1 KiB │   1.8 MiB │   1.8 MiB │   +8.1 KiB 
 manifest │   3.6 KiB │   3.6 KiB │      -1 B │    16 KiB │    16 KiB │        0 B 
      res │  10.2 MiB │  10.2 MiB │ +69.6 KiB │  24.2 MiB │  24.4 MiB │ +161.5 KiB 
   native │ 104.7 KiB │ 106.4 KiB │  +1.7 KiB │  36.5 KiB │  36.5 KiB │        0 B 
    asset │  51.8 KiB │  50.8 KiB │    -1 KiB │ 216.9 KiB │ 215.9 KiB │     -1 KiB 
    other │  46.9 KiB │  46.9 KiB │      -1 B │ 104.4 KiB │ 104.4 KiB │        0 B 
──────────┼───────────┼───────────┼───────────┼───────────┼───────────┼────────────
    total │  13.8 MiB │  13.9 MiB │ +78.5 KiB │  29.7 MiB │  29.8 MiB │ +169.3 KiB 

 DEX     │ old   │ new   │ diff             
─────────┼───────┼───────┼──────────────────
   files │     1 │     1 │  0               
 strings │ 14634 │ 14634 │  0 (+17 -17)     
   types │  5021 │  5020 │ -1 (+10 -11)     
 classes │  4122 │  4121 │ -1 (+3 -4)       
 methods │ 20965 │ 20968 │ +3 (+887 -884)   
  fields │ 14270 │ 14266 │ -4 (+1119 -1123) 

 ARSC    │ old   │ new   │ diff           
─────────┼───────┼───────┼────────────────
 configs │   148 │   148 │    0           
 entries │ 17224 │ 17340 │ +116 (+116 -0) 

Closes #466.