Implement linear and binary search

[mwermelinger]

Create a file paddles/search.py:

• Implement a linear search for an item in a sequence that may be unsorted.
• Implement a linear search in a sorted (non-decreasing) sequence.
• Implement a recursive binary search in a non-decreasing sequence. You may copy the code in Section 13.4.2 of the M269 book.
• Implement an iterative binary search. You may copy the code in Section 13.4.3 of the M269 book.
• The functions, except the first one, should raise ValueError if the sequence isn't non-decreasing.

Create a file tests/test_search.py that is similar to sorting.py:

• Create two constant lists, one of sorted sequences and another of unsorted sequences.
• Write a fixture sorted_sequence that returns one of the sorted sequences and a fixture any_sequence that returns either a sorted or unsorted sequence.
• Write a fixture search_sorted that returns a search function that works on sorted sequences and a fixture search_any that returns a search function that works on any sequence.
• Write two test functions: one applies search_sorted to sorted_sequence, the other applies search_any to any_sequence.