__repr__ for vso.attrs.Wave

[PritishC]

I've added a repr method similar to the one the Time class has, in the same package. This should resolve issue #532 that derdon had opened.

[coveralls]

Coverage remained the same when pulling 8cc991a on VaticanCameos:master into 6207c54 on sunpy:master.

[derdon]

Two tests are commented out and I proposed on IRC to use {2!r} instead of {2} to keep it consistent with Time.__repr__ and the classes which inherit from _VSOSimpleAttr.__repr__. Maybe even use {0:d} and {1:d} to make sure that min and max are integers.

[coveralls]

Coverage increased (+0.01%) when pulling 03a2fb4 on VaticanCameos:master into 6207c54 on sunpy:master.

[coveralls]

Coverage increased (+0.01%) when pulling 2247718 on VaticanCameos:master into 6207c54 on sunpy:master.

[Cadair]

Looks good to me. :)

[derdon]

The @pytest.fixture decorator does not make any sense here.

[coveralls]

Coverage remained the same when pulling 320f1ef on VaticanCameos:master into 6207c54 on sunpy:master.