Unset executable bits
lib: Add a hash table testing routine

This performs a simple stress test of a hash table, adding an order of
magnitude number of elements and then performing timed lookups. Example
output:

    0.000020 s        0.000002 s/entry        10 entries
    0.000432 s        0.000004 s/entry        100 entries
    0.030089 s        0.000030 s/entry        1000 entries
    3.330928 s        0.000333 s/entry        10000 entries
    390.718106 s      0.003907 s/entry        100000 entries

Required Hash table interface:

    HashTable(size)
    HashTable.set(key, value)
    HashTable.get(key)

If a key is not found, get() returns None.
05 - Add a Python Hash Table implementation