Fixes error when using to group_by_*

[leonelgalan]

Series was a range and needed to be converted to an array, this same conversion was done a couple of lines below. Closes #114

After posting the issue, I found out that the SQL was correct. Since this feature was added bd6b17d#diff-fa38e4a49c0b6d65a6d0a56acb87abf7R93 this line was missing the .to_a other lines had: bd6b17d#diff-fa38e4a49c0b6d65a6d0a56acb87abf7R107

Results for example posted in issue:

relation.group_by_hour_of_day(:created_at).group_by_day_of_week(:created_at).count
# => {[23, 0]=>186, [22, 0]=>337, [21, 0]=>539, [20, 0]=>602, [19, 0]=>1084, [18, 0]=>1270, [17, 0]=>1183, [16, 0]=>1337, [15, 0]=>1115, [14, 0]=>1376, [13, 0]=>1473, [12, 0]=>1495, [11, 0]=>776, [10, 0]=>393, [9, 0]=>293, [8, 0]=>214, [7, 0]=>78, [6, 0]=>55, [5, 0]=>49, [4, 0]=>23, [3, 0]=>47, [2, 0]=>134, [1, 0]=>151, [0, 0]=>341, [23, 1]=>226, [22, 1]=>300, [21, 1]=>505, [20, 1]=>803, [19, 1]=>1103, [18, 1]=>1584, [17, 1]=>1264, [16, 1]=>1028, [15, 1]=>1102, [14, 1]=>1340, [13, 1]=>1154, [12, 1]=>1130, [11, 1]=>840, [10, 1]=>669, [9, 1]=>326, [8, 1]=>244, [7, 1]=>236, [6, 1]=>93, [5, 1]=>83, [4, 1]=>38, [3, 1]=>15, [2, 1]=>8, [1, 1]=>40, [0, 1]=>148, [23, 2]=>205, [22, 2]=>403, [21, 2]=>934, [20, 2]=>1151, [19, 2]=>1373, [18, 2]=>1584, [17, 2]=>1373, [16, 2]=>1267, [15, 2]=>1306, [14, 2]=>1291, [13, 2]=>1087, [12, 2]=>1448, [11, 2]=>1155, [10, 2]=>842, [9, 2]=>361, [8, 2]=>289, [7, 2]=>239, [6, 2]=>94, [5, 2]=>141, [4, 2]=>21, [3, 2]=>8, [2, 2]=>5, [1, 2]=>65, [0, 2]=>111, [23, 3]=>258, [22, 3]=>379, [21, 3]=>817, [20, 3]=>1124, [19, 3]=>1337, [18, 3]=>1366, [17, 3]=>1161, [16, 3]=>1059, [15, 3]=>1343, [14, 3]=>1294, [13, 3]=>940, [12, 3]=>1472, [11, 3]=>1130, [10, 3]=>999, [9, 3]=>449, [8, 3]=>351, [7, 3]=>329, [6, 3]=>121, [5, 3]=>86, [4, 3]=>28, [3, 3]=>12, [2, 3]=>45, [1, 3]=>71, [0, 3]=>80, [23, 4]=>254, [22, 4]=>457, [21, 4]=>760, [20, 4]=>1122, [19, 4]=>1470, [18, 4]=>1702, [17, 4]=>1402, [16, 4]=>1192, [15, 4]=>1415, [14, 4]=>1444, [13, 4]=>1080, [12, 4]=>1368, [11, 4]=>1016, [10, 4]=>879, [9, 4]=>376, [8, 4]=>422, [7, 4]=>384, [6, 4]=>142, [5, 4]=>84, [4, 4]=>39, [3, 4]=>26, [2, 4]=>30, [1, 4]=>36, [0, 4]=>105, [23, 5]=>413, [22, 5]=>814, [21, 5]=>1449, [20, 5]=>1481, [19, 5]=>2049, [18, 5]=>2049, [17, 5]=>1669, [16, 5]=>1475, [15, 5]=>1308, [14, 5]=>1390, [13, 5]=>1292, [12, 5]=>1416, [11, 5]=>903, [10, 5]=>850, [9, 5]=>354, [8, 5]=>391, [7, 5]=>353, [6, 5]=>201, [5, 5]=>115, [4, 5]=>35, [3, 5]=>9, [2, 5]=>30, [1, 5]=>72, [0, 5]=>135, [23, 6]=>460, [22, 6]=>830, [21, 6]=>1090, [20, 6]=>1548, [19, 6]=>1856, [18, 6]=>2081, [17, 6]=>1725, [16, 6]=>1545, [15, 6]=>1369, [14, 6]=>1767, [13, 6]=>1738, [12, 6]=>1687, [11, 6]=>1126, [10, 6]=>644, [9, 6]=>435, [8, 6]=>352, [7, 6]=>177, [6, 6]=>75, [5, 6]=>70, [4, 6]=>36, [3, 6]=>8, [2, 6]=>108, [1, 6]=>140, [0, 6]=>283}

[ankane]

Great, thanks @leonelgalan! 👍 While investigating why this was calling reverse, I found another issue.