Avoid calling hyphenToCamelCase twice per note

[alexandermorgan]

hyphenToCamelCase from common.stringTools.py currently gets called twice for every note in a piece when importing an xml file. This can be avoided by passing an attributeName argument when using the _setAttributeFromTagText method to set the step and octave properties of notes.

With this change, when importing a file like:
score = corpus.parse('joplin/maple_leaf_rag.mxl', forceSource=True)
_setAttributeFromTagText goes from being called over 30k times to about 120 times. Since all the string manipulation in hyphenToCamelCase has no impact on one-word strings, all these avoided calls were unnecessary.

[coveralls]

coverage: 93.031% (+0.001%) from 93.03%
when pulling dbe9aab on alexandermorgan:master
into 3941a7f on cuthbertLab:master.

[jacobtylerwalls]

Thanks! Same spirit as 7a9a8f5.