Imports

Sets up sane default imports


```Python
In [1]: from blaze import *
csv = 
In [2]: csv = CSV('/home/mrocklin/data/bitcoin/data-code/user_edges.txt', 
          columns=['transaction', 'sender', 'recipient', 'timestamp', 'value'],
          hints={'timestamp': 'datetime'})

In [3]: t = Table(csv)

In [4]: t
Out[4]: 
   transaction   sender  recipient       timestamp       value
0            1        2          2  20130410142250   24.375000
1            1        2     782477  20130410142250    0.770900
2            2   620423    4571210  20111227114312  614.174951
3            2   620423          3  20111227114312  128.040520
4            3        3     782479  20130410142250   47.140520
5            3        3          4  20130410142250  150.000000
6            4    39337      39337  20120617120202    0.310818
7            4    39337          3  20120617120202   69.100000
8            5  2071196    2070358  20130304143805   61.602352
9            5  2071196          5  20130304143805  100.000000

[10 rows x 5 columns]
...
In [7]: from blaze.sql import *

In [8]: sql = SQL('sqlite:///btc.db', 'user_edges')

In [9]: s = Table(sql)

In [10]: s
Out[10]: 
   transaction   sender  recipient                date       value
0            1        2          2 2013-04-10 14:22:50   24.375000
1            1        2     782477 2013-04-10 14:22:50    0.770900
2            2   620423    4571210 2011-12-27 11:43:12  614.174951
3            2   620423          3 2011-12-27 11:43:12  128.040520
4            3        3     782479 2013-04-10 14:22:50   47.140520
5            3        3          4 2013-04-10 14:22:50  150.000000
6            4    39337      39337 2012-06-17 12:02:02    0.310818
7            4    39337          3 2012-06-17 12:02:02   69.100000
8            5  2071196    2070358 2013-03-04 14:38:05   61.602352
9            5  2071196          5 2013-03-04 14:38:05  100.000000

[10 rows x 5 columns]
...
```

TODO: This currently breaks the Spark backend because we can't send any functions down Spark pipes that include anything having to do with Pandas.  Because Blaze imports pandas by default no code even remotely related to Blaze code can be serialized.