Utilities for using and plotting obspy.Stream classes

Linking this fella [here](https://github.com/obspy/obspy/issues/607#issuecomment-23674138)

Quoting obspy developer code about how simple is to use Stream to create from an array 

>     from obspy import Stream, Trace, read
>     from obspy.core import AttribDict
>     import numpy as np
>
>     st = Stream(traces=Trace(data=np.empty(10, dtype='float32'),
>            header={'delta': 0.004}))
>     # Create SEGY Trace header to write SEGY specific header values.
>     st[0].stats.segy = AttribDict()
>     st[0].stats.segy.trace_header = AttribDict()
>     st[0].stats.segy.trace_header.uphole_time_at_group_in_ms = 66

>     st.write("test.segy", format="SEGY")
>     st2 = read("test.segy")
>     print st2[0].stats.delta
>     print st2[0].stats.segy.trace_header.uphole_time_at_group_in_ms

And closed [PR 27](https://github.com/leouieda/fatiando/pull/27)