Fixes in the npyio documentation

Fixes the "see also" section of savetxt, which
described savez as compressing (closes #587 ). Also
replaces all occurences of .npy and .npz to use double backticks.
Some had, some did not, and some had " symbols.
small typo
BUG: fix #3017 Inconsistency in indexing 0-d arrays with Ellipsis.
BLD: fix Bento build.

Issue was introduced with PR-3524, the ufunc override stuff.
BLD: add new test extensions (rational, struct_ufunc, operand_flag) to Bento build.
TST: exercise median of median of 5 code by using a median of 3 killer dataset
ENH: remove an always true conditional

v[1] < v[2] is guaranteed by the swapping a few lines above
DOC STY: make npyio docstrings less than 80 chars
BUG: make checking for sse intrinsics more robust

check for two intrinsics from [ex]mmintrin.h instead of only checking
the existance of the headers.
E.g. mingw 4.2 emmintrin.h can be included even if SSE2 is disabled.
closes #3760
Merge pull request #3753 from jarondl/fix-doc-savetxt

DOC: Fixes in the npyio documentation
ENH: Add gfortran to travis.yml configuration to enable f2py tests.
Merge pull request #3773 from charris/enable-f2py-tests

ENH: Add gfortran to travis.yml configuration to enable f2py tests.
DOC: [bento] document that adding optional GCC performance improvements is TODO

[ci skip]
BUG: core: don't ignore raised exceptions in __numpy_ufunc__ handler
REF: core: clean up PyUFunc_CheckOverride

Move argument normalization out from the inner loop, reduce complexity.
Add error checks.
Merge pull request #3777 from pv/ufunc-override-fix

BUG: core: don't ignore raised exceptions in __numpy_ufunc__ handler
Merge pull request #3767 from juliantaylor/mom5-improve

Mom5 selection improvements
ENH: Added test cases for relation operation. To ensure behaviour of int. There is a need to add test case which ensure and maintain the behaviour of integer. As per pr #3567, which speed up integer scalar's operations by avoiding the conversion of integer to NumPy Scalar.
scalar relational operation
Moved test_multiarra_relational_operators to test_multiarray.py