add a test file for GSE2 with STA2 header

this comes from an independent source, the actual values were changed so
that the original data is not recognizable anymore but the positioning
in the STA2 header line is unchanged.
Merge remote-tracking branch 'upstream/master' into fix_gse2_sta2
basics for reading/writing STA2 line in GSE2
fix syntax of #670 for python 2.6
some Py 2.6 unittest fixes
GSE2/STA2: adjust parsing of STA2 line

All fields up to the last two adhere to fixed format columns in all
files I've seen so far, so used fixed columns for parsing them.
GSE2/STA2: adjustments to parsing/compiling STA2 line
GSE2/STA2: adjust some test files

They did not adhere to STA2 line definition (in latitude field, can not
be represented according to format given by manual)
need to update scan.png baseline image

one file now has network parsed from STA2, one new file in gse2 test
data.
image tests: higher tolerance for 3 tests on very old matplotlib

I checked all three, the axis box gets plotted slightly differently for them on matplotlib 1.1.1 but that's not our problem.
Merge pull request #641 from obspy/fix_gse2_sta2

STA2 header line of GSE2 files
Merge branch 'master' into travis_py2.6_rebased