Fix ZBase32.encode() and decode() and write passing tests against spec examples

[jiyoontbd]

Currently tests for these are failing when using tests per the spec examples.

EXAMPLES

#bits base-2                           base32     base64     z-base-32
----- ------                           ------     ------     ---------
1     0                                AA======   AA==       y
1     1                                QA======   gA==       o
2     01                               IA======   QA==       e
2     11                               QA======   gA==       a
10    0000000000                       AAAA====   AAA=       yy
10    1000000010                       QCAA====   gIA=       on
20    10001011100010001000             BC4IQ===   CLiI       tqre
24    111100001011111111000111         6C74O===   8L/H       6n9hq
24    110101000111101000000100         2R5AI===   1HoE       4t7ye
30    111101010101011110111101000011   HVK66QY=   PVXvQw==   6im5sd

Need to write passing tests for ZBase32Test.kt and ConvertTest#toZBase32