use "1p0" instead of "1.0" in lti_version

Spec details here:

http://www.imsglobal.org/lti/blti/bltiv1p0/ltiBLTIimgv1p0.html#_Toc261271975
Merge pull request #5 from whitmer/master

Change "1.0" to "1p0" in lti_version, as per the spec