Use a release version of Eigen for building Python package. (#608)
Use a release version of Eigen for building Python package. (#608)

* Remove need for hg for building Python package by using an Eigen release.

* Fixed some bugs


Former-commit-id: d160a7b3f665efb94cb4115c8069e3d2b262204e
clab/dynet,clab/cnn,clab/cnn,shuheik/dynet,clab/dynet,chunyang-wen/dynet,clab/dynet,shuheik/dynet,xunzhang/dynet,shuheik/dynet,xunzhang/dynet,clab/dynet,clab/dynet,danielhers/dynet,xunzhang/dynet,shuheik/dynet,shuheik/dynet,chunyang-wen/dynet,danielhers/dynet,xunzhang/dynet,chunyang-wen/dynet,danielhers/dynet,clab/cnn,danielhers/dynet,chunyang-wen/dynet,clab/dynet,danielhers/dynet,shuheik/dynet,shuheik/dynet,clab/dynet,danielhers/dynet,danielhers/dynet